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Helium

May 11, 2023

This article is about the chemical element. For other uses, see Helium (disambiguation).

Helium (from Greek: ἥλιος, romanized: helios, lit. 'sun') is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table.[a] Its boiling point is the lowest among all the elements, and it does not have a melting point at standard pressure. It is the second lightest and second most abundant element in the observable universe, after hydrogen. It is present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this in both the Sun and in Jupiter, due to the very high nuclear binding energy (per nucleon) of helium-4, with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of both nuclear fusion and radioactive decay. The most common isotope of helium in the universe is helium-4, the vast majority of which was formed during the Big Bang. Large amounts of new helium are created by nuclear fusion of hydrogen in stars.

Helium, 2He
Helium
Pronunciation/ˈhiːliəm/ ​(HEE-lee-əm)
Appearancecolorless gas, exhibiting a gray, cloudy glow (or reddish-orange if an especially high voltage is used) when placed in an electric field
Standard atomic weight Ar°(He)
  • 4.002602±0.000002
  • 4.0026±0.0001 (abridged)[1]
Helium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
–
↑
He
↓
Ne
hydrogen ← helium → lithium
Atomic number (Z)2
Groupgroup 18 (noble gases)
Periodperiod 1
Block  s-block
Electron configuration1s2
Electrons per shell2
Physical properties
Phase at STPgas
Melting point0.95 K ​(−272.20 °C, ​−457.96 °F) (at 2.5 MPa)
Boiling point4.222 K ​(−268.928 °C, ​−452.070 °F)
Density (at STP)0.1786 g/L
when liquid (at m.p.)0.145 g/cm3
when liquid (at b.p.)0.125 g/cm3
Triple point2.177 K, ​5.043 kPa
Critical point5.1953 K, 0.22746 MPa
Heat of fusion0.0138 kJ/mol
Heat of vaporization0.0829 kJ/mol
Molar heat capacity20.78 J/(mol·K)[2]
Vapor pressure (defined by ITS-90)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K)     1.23 1.67 2.48 4.21
Atomic properties
Oxidation states0
ElectronegativityPauling scale: no data
Ionization energies
  • 1st: 2372.3 kJ/mol
  • 2nd: 5250.5 kJ/mol
Covalent radius28 pm
Van der Waals radius140 pm
Spectral lines of helium
Other properties
Natural occurrenceprimordial
Crystal structure ​hexagonal close-packed (hcp)
Speed of sound972 m/s
Thermal conductivity0.1513 W/(m⋅K)
Magnetic orderingdiamagnetic[3]
Molar magnetic susceptibility−1.88×10−6 cm3/mol (298 K)[4]
CAS Number7440-59-7
History
Namingafter Helios, Greek god of the Sun
DiscoveryPierre Janssen, Norman Lockyer (1868)
First isolationWilliam Ramsay, Per Teodor Cleve, Abraham Langlet (1895)
Isotopes of helium
Main isotopes[5] Decay
abun­dance half-life (t1/2) mode pro­duct
3He 0.0002% stable
4He 99.9998% stable
 Category: Helium
| references

Helium was first detected as an unknown, yellow spectral line signature in sunlight during a solar eclipse in 1868 by Georges Rayet,[12] Captain C. T. Haig,[13] Norman R. Pogson,[14] and Lieutenant John Herschel,[15] and was subsequently confirmed by French astronomer Jules Janssen.[16] Janssen is often jointly credited with detecting the element, along with Norman Lockyer. Janssen recorded the helium spectral line during the solar eclipse of 1868, while Lockyer observed it from Britain. Lockyer was the first to propose that the line was due to a new element, which he named after the sun. The formal discovery of the element was made in 1895 by chemists Sir William Ramsay, Per Teodor Cleve, and Nils Abraham Langlet, who found helium emanating from the uranium ore, cleveite, which is now not regarded as a separate mineral species, but as a variety of uraninite.[17][18] In 1903, large reserves of helium were found in natural gas fields in parts of the United States, by far the largest supplier of the gas today.

Liquid helium is used in cryogenics (its largest single use, consuming about a quarter of production), and in the cooling of superconducting magnets, with its main commercial application in MRI scanners. Helium's other industrial uses—as a pressurizing and purge gas, as a protective atmosphere for arc welding, and in processes such as growing crystal to make silicon wafers—account for half of the gas produced. A small but well-known use is as a lifting gas in balloons and airships.[19] As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice. In scientific research, the behavior of the two fluid phases of helium-4 (helium I and helium II) is important to researchers studying quantum mechanics (in particular the property of superfluidity) and to those looking at the phenomena, such as superconductivity, produced in matter near absolute zero.

On Earth, it is relatively rare—5.2 ppm by volume in the atmosphere. Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements (thorium and uranium, although there are other examples), as the alpha particles emitted by such decays consist of helium-4 nuclei. This radiogenic helium is trapped with natural gas in concentrations as great as 7% by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation. Terrestrial helium is a non-renewable resource because once released into the atmosphere, it promptly escapes into space. Its supply is thought to be rapidly diminishing.[20][21] However, some studies suggest that helium produced deep in the earth by radioactive decay can collect in natural gas reserves in larger than expected quantities,[22] in some cases, having been released by volcanic activity.[23]

History

Scientific discoveries

The first evidence of helium was observed on August 18, 1868, as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun. The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India.[24][25] This line was initially assumed to be sodium. On October 20 of the same year, English astronomer, Norman Lockyer, observed a yellow line in the solar spectrum, which, he named the D3 because it was near the known D1 and D2 Fraunhofer line lines of sodium.[26][27] He concluded that it was caused by an element in the Sun unknown on Earth. Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος (helios).[28][29]

 
Spectral lines of helium

In 1881, Italian physicist Luigi Palmieri detected helium on Earth for the first time through its D3 spectral line, when he analyzed a material that had been sublimated during a recent eruption of Mount Vesuvius.[30]

 
Sir William Ramsay, the discoverer of terrestrial helium
 
The cleveite sample from which Ramsay first purified helium[31]

On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% rare-earth elements) with mineral acids. Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas, liberated by sulfuric acid, he noticed a bright yellow line that matched the D3 line observed in the spectrum of the Sun.[27][32][33][34] These samples were identified as helium by Lockyer and British physicist William Crookes.[35][36] It was independently isolated from cleveite, in the same year, by chemists, Per Teodor Cleve and Abraham Langlet, in Uppsala, Sweden, who collected enough of the gas to accurately determine its atomic weight.[37][38][25][39] Helium was also isolated by the American geochemist, William Francis Hillebrand, prior to Ramsay's discovery, when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed the lines to nitrogen.[40] His letter of congratulations to Ramsay offers an interesting case of discovery, and near-discovery, in science.[41]

In 1907, Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei, by allowing the particles to penetrate the thin, glass wall of an evacuated tube, then creating a discharge in the tube, to study the spectrum of the new gas inside.[42] In 1908, helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than 5 K (−268.15 °C; −450.67 °F).[43][44] He tried to solidify it, by further reducing the temperature, but failed, because helium does not solidify at atmospheric pressure. Onnes' student Willem Hendrik Keesom was eventually able to solidify 1 cm3 of helium in 1926 by applying additional external pressure.[45][46]

In 1913, Niels Bohr published his "trilogy"[47][48] on atomic structure that included a reconsideration of the Pickering–Fowler series as central evidence in support of his model of the atom.[49][50] This series is named for Edward Charles Pickering, who in 1896 published observations of previously unknown lines in the spectrum of the star ζ Puppis[51] (these are now known to occur with Wolf–Rayet and other hot stars).[52] Pickering attributed the observation (lines at 4551, 5411, and 10123 Å) to a new form of hydrogen with half-integer transition levels.[53][54] In 1912, Alfred Fowler[55] managed to produce similar lines from a hydrogen-helium mixture, and supported Pickering's conclusion as to their origin.[56] Bohr's model does not allow for half-integer transitions (nor does quantum mechanics) and Bohr concluded that Pickering and Fowler were wrong, and instead assigned these spectral lines to ionised helium, He+.[57] Fowler was initially skeptical[58] but was ultimately convinced[59] that Bohr was correct,[47] and by 1915 "spectroscopists had transferred [the Pickering–Fowler series] definitively [from hydrogen] to helium."[50][60] Bohr's theoretical work on the Pickering series had demonstrated the need for "a re-examination of problems that seemed already to have been solved within classical theories" and provided important confirmation for his atomic theory.[50]

In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at temperatures near absolute zero, a phenomenon now called superfluidity.[61] This phenomenon is related to Bose–Einstein condensation. In 1972, the same phenomenon was observed in helium-3, but at temperatures much closer to absolute zero, by American physicists Douglas D. Osheroff, David M. Lee, and Robert C. Richardson. The phenomenon in helium-3 is thought to be related to pairing of helium-3 fermions to make bosons, in analogy to Cooper pairs of electrons producing superconductivity.[62]

Extraction and use

 
Historical marker, denoting a massive helium find near Dexter, Kansas

After an oil drilling operation in 1903 in Dexter, Kansas produced a gas geyser that would not burn, Kansas state geologist Erasmus Haworth collected samples of the escaping gas and took them back to the University of Kansas at Lawrence where, with the help of chemists Hamilton Cady and David McFarland, he discovered that the gas consisted of, by volume, 72% nitrogen, 15% methane (a combustible percentage only with sufficient oxygen), 1% hydrogen, and 12% an unidentifiable gas.[25][63] With further analysis, Cady and McFarland discovered that 1.84% of the gas sample was helium.[64][65] This showed that despite its overall rarity on Earth, helium was concentrated in large quantities under the American Great Plains, available for extraction as a byproduct of natural gas.[66]

This enabled the United States to become the world's leading supplier of helium. Following a suggestion by Sir Richard Threlfall, the United States Navy sponsored three small experimental helium plants during World War I. The goal was to supply barrage balloons with the non-flammable, lighter-than-air gas. A total of 5,700 m3 (200,000 cu ft) of 92% helium was produced in the program even though less than a cubic meter of the gas had previously been obtained.[27] Some of this gas was used in the world's first helium-filled airship, the U.S. Navy's C-class blimp C-7, which flew its maiden voyage from Hampton Roads, Virginia, to Bolling Field in Washington, D.C., on December 1, 1921,[67] nearly two years before the Navy's first rigid helium-filled airship, the Naval Aircraft Factory-built USS Shenandoah, flew in September 1923.

Although the extraction process using low-temperature gas liquefaction was not developed in time to be significant during World War I, production continued. Helium was primarily used as a lifting gas in lighter-than-air craft. During World War II, the demand increased for helium for lifting gas and for shielded arc welding. The helium mass spectrometer was also vital in the atomic bomb Manhattan Project.[68]

The government of the United States set up the National Helium Reserve in 1925 at Amarillo, Texas, with the goal of supplying military airships in time of war and commercial airships in peacetime.[27] Because of the Helium Act of 1925, which banned the export of scarce helium on which the US then had a production monopoly, together with the prohibitive cost of the gas, German Zeppelins was forced to use hydrogen as lifting gas, which would gain infamy in the Hindenburg disaster. The helium market after World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen/hydrogen rocket fuel (among other uses) during the Space Race and Cold War. Helium use in the United States in 1965 was more than eight times the peak wartime consumption.[69]

After the "Helium Acts Amendments of 1960" (Public Law 86–777), the U.S. Bureau of Mines arranged for five private plants to recover helium from natural gas. For this helium conservation program, the Bureau built a 425-mile (684 km) pipeline from Bushton, Kansas, to connect those plants with the government's partially depleted Cliffside gas field near Amarillo, Texas. This helium-nitrogen mixture was injected and stored in the Cliffside gas field until needed, at which time it was further purified.[70]

By 1995, a billion cubic meters of the gas had been collected and the reserve was US$1.4 billion in debt, prompting the Congress of the United States in 1996 to discontinue the reserve.[25][71] The resulting Helium Privatization Act of 1996[72] (Public Law 104–273) directed the United States Department of the Interior to empty the reserve, with sales starting by 2005.[73]

Helium produced between 1930 and 1945 was about 98.3% pure (2% nitrogen), which was adequate for airships. In 1945, a small amount of 99.9% helium was produced for welding use. By 1949, commercial quantities of Grade A 99.95% helium were available.[74]

For many years, the United States produced more than 90% of commercially usable helium in the world, while extraction plants in Canada, Poland, Russia, and other nations produced the remainder. In the mid-1990s, a new plant in Arzew, Algeria, producing 17 million cubic meters (600 million cubic feet) began operation, with enough production to cover all of Europe's demand. Meanwhile, by 2000, the consumption of helium within the U.S. had risen to more than 15 million kg per year.[75] In 2004–2006, additional plants in Ras Laffan, Qatar, and Skikda, Algeria were built. Algeria quickly became the second leading producer of helium.[76] Through this time, both helium consumption and the costs of producing helium increased.[77] From 2002 to 2007 helium prices doubled.[78]

As of 2012, the United States National Helium Reserve accounted for 30 percent of the world's helium.[79] The reserve was expected to run out of helium in 2018.[79] Despite that, a proposed bill in the United States Senate would allow the reserve to continue to sell the gas. Other large reserves were in the Hugoton in Kansas, United States, and nearby gas fields of Kansas and the panhandles of Texas and Oklahoma. New helium plants were scheduled to open in 2012 in Qatar, Russia, and the US state of Wyoming, but they were not expected to ease the shortage.[79]

In 2013, Qatar started up the world's largest helium unit,[80] although the 2017 Qatar diplomatic crisis severely affected helium production there.[81] 2014 was widely acknowledged to be a year of over-supply in the helium business, following years of renowned shortages.[82] Nasdaq reported (2015) that for Air Products, an international corporation that sells gases for industrial use, helium volumes remain under economic pressure due to feedstock supply constraints.[83]

(Also, see the sub-section Conservation advocates in this article’s section Occurrence and production, below.)

Characteristics

Atom

Main article: Helium atom
 
The helium atom. Depicted are the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case.

In quantum mechanics

In the perspective of quantum mechanics, helium is the second simplest atom to model, following the hydrogen atom. Helium is composed of two electrons in atomic orbitals surrounding a nucleus containing two protons and (usually) two neutrons. As in Newtonian mechanics, no system that consists of more than two particles can be solved with an exact analytical mathematical approach (see 3-body problem) and helium is no exception. Thus, numerical mathematical methods are required, even to solve the system of one nucleus and two electrons. Such computational chemistry methods have been used to create a quantum mechanical picture of helium electron binding which is accurate to within < 2% of the correct value, in a few computational steps.[84] Such models show that each electron in helium partly screens the nucleus from the other, so that the effective nuclear charge Zeff which each electron sees is about 1.69 units, not the 2 charges of a classic "bare" helium nucleus.

Related stability of the helium-4 nucleus and electron shell

The nucleus of the helium-4 atom is identical with an alpha particle. High-energy electron-scattering experiments show its charge to decrease exponentially from a maximum at a central point, exactly as does the charge density of helium's own electron cloud. This symmetry reflects similar underlying physics: the pair of neutrons and the pair of protons in helium's nucleus obey the same quantum mechanical rules as do helium's pair of electrons (although the nuclear particles are subject to a different nuclear binding potential), so that all these fermions fully occupy 1s orbitals in pairs, none of them possessing orbital angular momentum, and each cancelling the other's intrinsic spin. Adding another of any of these particles would require angular momentum and would release substantially less energy (in fact, no nucleus with five nucleons is stable). This arrangement is thus energetically extremely stable for all these particles, and this stability accounts for many crucial facts regarding helium in nature.

For example, the stability and low energy of the electron cloud state in helium accounts for the element's chemical inertness, and also the lack of interaction of helium atoms with each other, producing the lowest melting and boiling points of all the elements.

In a similar way, the particular energetic stability of the helium-4 nucleus, produced by similar effects, accounts for the ease of helium-4 production in atomic reactions that involve either heavy-particle emission or fusion. Some stable helium-3 (two protons and one neutron) is produced in fusion reactions from hydrogen, but it is a very small fraction compared to the highly favorable helium-4.

 
Binding energy per nucleon of common isotopes. The binding energy per particle of helium-4 is significantly larger than all nearby nuclides.

The unusual stability of the helium-4 nucleus is also important cosmologically: it explains the fact that in the first few minutes after the Big Bang, as the "soup" of free protons and neutrons which had initially been created in about 6:1 ratio cooled to the point that nuclear binding was possible, almost all first compound atomic nuclei to form were helium-4 nuclei. Owing to the relatively tight binding of helium-4 nuclei, its production consumed nearly all of the free neutrons in a few minutes, before they could beta-decay, and thus few neutrons were available to form heavier atoms such as lithium, beryllium, or boron. Helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis and binding energy) and thus, once helium had been formed, no energetic drive was available to make elements 3, 4 and 5.[85] It is barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon, carbon. However, due to lack of intermediate elements, this process requires three helium nuclei striking each other nearly simultaneously (see triple alpha process). There was thus no time for significant carbon to be formed in the few minutes after the Big Bang, before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible. This left the early universe with a very similar ratio of hydrogen/helium as is observed today (3 parts hydrogen to 1 part helium-4 by mass), with nearly all the neutrons in the universe trapped in helium-4.

All heavier elements (including those necessary for rocky planets like the Earth, and for carbon-based or other life) have thus been created since the Big Bang in stars which were hot enough to fuse helium itself. All elements other than hydrogen and helium today account for only 2% of the mass of atomic matter in the universe. Helium-4, by contrast, makes up about 23% of the universe's ordinary matter—nearly all the ordinary matter that is not hydrogen.

Gas and plasma phases

 
Helium discharge tube shaped into 'He', the element's symbol.

Helium is the second least reactive noble gas after neon, and thus the second least reactive of all elements.[86] It is chemically inert and monatomic in all standard conditions. Because of helium's relatively low molar (atomic) mass, its thermal conductivity, specific heat, and sound speed in the gas phase are all greater than any other gas except hydrogen. For these reasons and the small size of helium monatomic molecules, helium diffuses through solids at a rate three times that of air and around 65% that of hydrogen.[27]

Helium is the least water-soluble monatomic gas,[87] and one of the least water-soluble of any gas (CF4, SF6, and C4F8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x2/10−5, respectively, versus helium's 0.70797 x2/10−5),[88] and helium's index of refraction is closer to unity than that of any other gas.[89] Helium has a negative Joule–Thomson coefficient at normal ambient temperatures, meaning it heats up when allowed to freely expand. Only below its Joule–Thomson inversion temperature (of about 32 to 50 K at 1 atmosphere) does it cool upon free expansion.[27] Once precooled below this temperature, helium can be liquefied through expansion cooling.

Most extraterrestrial helium is plasma in stars, with properties quite different from those of atomic helium. In a plasma, helium's electrons are not bound to its nucleus, resulting in very high electrical conductivity, even when the gas is only partially ionized. The charged particles are highly influenced by magnetic and electric fields. For example, in the solar wind together with ionized hydrogen, the particles interact with the Earth's magnetosphere, giving rise to Birkeland currents and the aurora.[90]

Liquid phase

Main article: Liquid helium
 
Liquefied helium. This helium is not only liquid, but has been cooled to the point of superfluidity. The drop of liquid at the bottom of the glass represents helium spontaneously escaping from the container over the side, to empty out of the container. The energy to drive this process is supplied by the potential energy of the falling helium.

Unlike any other element, helium will remain liquid down to absolute zero at normal pressures. This is a direct effect of quantum mechanics: specifically, the zero point energy of the system is too high to allow freezing. Solid helium requires a temperature of 1–1.5 K (about −272 °C or −457 °F) at about 25 bar (2.5 MPa) of pressure.[91] It is often hard to distinguish solid from liquid helium since the refractive index of the two phases are nearly the same. The solid has a sharp melting point and has a crystalline structure, but it is highly compressible; applying pressure in a laboratory can decrease its volume by more than 30%.[92] With a bulk modulus of about 27 MPa[93] it is ~100 times more compressible than water. Solid helium has a density of 0.214±0.006 g/cm3 at 1.15 K and 66 atm; the projected density at 0 K and 25 bar (2.5 MPa) is 0.187±0.009 g/cm3.[94] At higher temperatures, helium will solidify with sufficient pressure. At room temperature, this requires about 114,000 atm.[95]

Helium I

Below its boiling point of 4.22 K (−268.93 °C; −452.07 °F) and above the lambda point of 2.1768 K (−270.9732 °C; −455.7518 °F), the isotope helium-4 exists in a normal colorless liquid state, called helium I.[27] Like other cryogenic liquids, helium I boils when it is heated and contracts when its temperature is lowered. Below the lambda point, however, helium does not boil, and it expands as the temperature is lowered further.

Helium I has a gas-like index of refraction of 1.026 which makes its surface so hard to see that floats of Styrofoam are often used to show where the surface is.[27] This colorless liquid has a very low viscosity and a density of 0.145–0.125 g/mL (between about 0 and 4 K),[96] which is only one-fourth the value expected from classical physics.[27] Quantum mechanics is needed to explain this property and thus both states of liquid helium (helium I and helium II) are called quantum fluids, meaning they display atomic properties on a macroscopic scale. This may be an effect of its boiling point being so close to absolute zero, preventing random molecular motion (thermal energy) from masking the atomic properties.[27]

Helium II

Main article: Superfluid helium-4

Liquid helium below its lambda point (called helium II) exhibits very unusual characteristics. Due to its high thermal conductivity, when it boils, it does not bubble but rather evaporates directly from its surface. Helium-3 also has a superfluid phase, but only at much lower temperatures; as a result, less is known about the properties of the isotope.[27]

 
Unlike ordinary liquids, helium II will creep along surfaces in order to reach an equal level; after a short while, the levels in the two containers will equalize. The Rollin film also covers the interior of the larger container; if it were not sealed, the helium II would creep out and escape.[27]

Helium II is a superfluid, a quantum mechanical state (see: macroscopic quantum phenomena) of matter with strange properties. For example, when it flows through capillaries as thin as 10−7 to 10−8 m it has no measurable viscosity.[25] However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium was observed. Current theory explains this using the two-fluid model for helium II. In this model, liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a ground state, which are superfluid and flow with exactly zero viscosity, and a proportion of helium atoms in an excited state, which behave more like an ordinary fluid.[97]

In the fountain effect, a chamber is constructed which is connected to a reservoir of helium II by a sintered disc through which superfluid helium leaks easily but through which non-superfluid helium cannot pass. If the interior of the container is heated, the superfluid helium changes to non-superfluid helium. In order to maintain the equilibrium fraction of superfluid helium, superfluid helium leaks through and increases the pressure, causing liquid to fountain out of the container.[98]

The thermal conductivity of helium II is greater than that of any other known substance, a million times that of helium I and several hundred times that of copper.[27] This is because heat conduction occurs by an exceptional quantum mechanism. Most materials that conduct heat well have a valence band of free electrons which serve to transfer the heat. Helium II has no such valence band but nevertheless conducts heat well. The flow of heat is governed by equations that are similar to the wave equation used to characterize sound propagation in air. When heat is introduced, it moves at 20 meters per second at 1.8 K through helium II as waves in a phenomenon known as second sound.[27]

Helium II also exhibits a creeping effect. When a surface extends past the level of helium II, the helium II moves along the surface, against the force of gravity. Helium II will escape from a vessel that is not sealed by creeping along the sides until it reaches a warmer region where it evaporates. It moves in a 30 nm-thick film regardless of surface material. This film is called a Rollin film and is named after the man who first characterized this trait, Bernard V. Rollin.[27][99][100] As a result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, it is very difficult to confine. Unless the container is carefully constructed, the helium II will creep along the surfaces and through valves until it reaches somewhere warmer, where it will evaporate. Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity, the restoring force is the van der Waals force.[101] These waves are known as third sound.[102]

Isotopes

Main article: Isotopes of helium

There are nine known isotopes of helium of which two, helium-3 and helium-4, are stable. In the Earth's atmosphere, one atom is 3
He for every million that are 4
He.[25] Unlike most elements, helium's isotopic abundance varies greatly by origin, due to the different formation processes. The most common isotope, helium-4, is produced on Earth by alpha decay of heavier radioactive elements; the alpha particles that emerge are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its nucleons are arranged into complete shells. It was also formed in enormous quantities during Big Bang nucleosynthesis.[103]

Helium-3 is present on Earth only in trace amounts. Most of it has been present since Earth's formation, though some falls to Earth trapped in cosmic dust.[104] Trace amounts are also produced by the beta decay of tritium.[105] Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten, and these ratios can be used to investigate the origin of rocks and the composition of the Earth's mantle.[104] 3
He is much more abundant in stars as a product of nuclear fusion. Thus in the interstellar medium, the proportion of 3
He to 4
He is about 100 times higher than on Earth.[106] Extraplanetary material, such as lunar and asteroid regolith, have trace amounts of helium-3 from being bombarded by solar winds. The Moon's surface contains helium-3 at concentrations on the order of 10 ppb, much higher than the approximately 5 ppt found in the Earth's atmosphere.[107][108] A number of people, starting with Gerald Kulcinski in 1986,[109] have proposed to explore the moon, mine lunar regolith, and use the helium-3 for fusion.

Liquid helium-4 can be cooled to about 1 K (−272.15 °C; −457.87 °F) using evaporative cooling in a 1-K pot. Similar cooling of helium-3, which has a lower boiling point, can achieve about 0.2 kelvin in a helium-3 refrigerator. Equal mixtures of liquid 3
He and 4
He below 0.8 K separate into two immiscible phases due to their dissimilarity (they follow different quantum statistics: helium-4 atoms are bosons while helium-3 atoms are fermions).[27] Dilution refrigerators use this immiscibility to achieve temperatures of a few millikelvins.[110]

It is possible to produce exotic helium isotopes, which rapidly decay into other substances. The shortest-lived heavy helium isotope is the unbound helium-10 with a half-life of 2.6(4)×10−22 s.[5] Helium-6 decays by emitting a beta particle and has a half-life of 0.8 second. Helium-7 and helium-8 are created in certain nuclear reactions.[27] Helium-6 and helium-8 are known to exhibit a nuclear halo.[27]

Properties

Table of thermal and physical properties of helium gas at atmospheric pressure:[111][112]

Temperature (K) Density (kg/m^3) Specific heat (kJ/kg °C) Dynamic viscosity (kg/m s) Kinematic viscosity (m^2/s) Thermal conductivity (W/m °C) Thermal diffusivity (m^2/s) Prandtl Number
100 5.193 9.63E-06 1.98E-05 0.073 2.89E-05 0.686
120 0.406 5.193 1.07E-05 2.64E-05 0.0819 3.88E-05 0.679
144 0.3379 5.193 1.26E-05 3.71E-05 0.0928 5.28E-05 0.7
200 0.2435 5.193 1.57E-05 6.44E-05 0.1177 9.29E-05 0.69
255 0.1906 5.193 1.82E-05 9.55E-05 0.1357 1.37E-04 0.7
366 0.1328 5.193 2.31E-05 1.74E-04 0.1691 2.45E-04 0.71
477 0.10204 5.193 2.75E-05 2.69E-04 0.197 3.72E-04 0.72
589 0.08282 5.193 3.11E-05 3.76E-04 0.225 5.22E-04 0.72
700 0.07032 5.193 3.48E-05 4.94E-04 0.251 6.66E-04 0.72
800 0.06023 5.193 3.82E-05 6.34E-04 0.275 8.77E-04 0.72
900 0.05451 5.193 4.14E-05 7.59E-04 0.33 1.14E-03 0.687
1000 5.193 4.46E-05 9.14E-04 0.354 1.40E-03 0.654

Compounds

Main article: Helium compounds
 
Structure of the helium hydride ion, HHe+
 
Structure of the suspected fluoroheliate anion, OHeF−

Helium has a valence of zero and is chemically unreactive under all normal conditions.[92] It is an electrical insulator unless ionized. As with the other noble gases, helium has metastable energy levels that allow it to remain ionized in an electrical discharge with a voltage below its ionization potential.[27] Helium can form unstable compounds, known as excimers, with tungsten, iodine, fluorine, sulfur, and phosphorus when it is subjected to a glow discharge, to electron bombardment, or reduced to plasma by other means. The molecular compounds HeNe, HgHe10, and WHe2, and the molecular ions He+
2, He2+
2, HeH+
, and HeD+
 have been created this way.[113] HeH+ is also stable in its ground state, but is extremely reactive—it is the strongest Brønsted acid known, and therefore can exist only in isolation, as it will protonate any molecule or counteranion it contacts. This technique has also produced the neutral molecule He2, which has a large number of band systems, and HgHe, which is apparently held together only by polarization forces.[27]

Van der Waals compounds of helium can also be formed with cryogenic helium gas and atoms of some other substance, such as LiHe and He2.[114]

Theoretically, other true compounds may be possible, such as helium fluorohydride (HHeF) which would be analogous to HArF, discovered in 2000.[115] Calculations show that two new compounds containing a helium-oxygen bond could be stable.[116] Two new molecular species, predicted using theory, CsFHeO and N(CH3)4FHeO, are derivatives of a metastable FHeO− anion first theorized in 2005 by a group from Taiwan. If confirmed by experiment, the only remaining element with no known stable compounds would be neon.[117]

Helium atoms have been inserted into the hollow carbon cage molecules (the fullerenes) by heating under high pressure. The endohedral fullerene molecules formed are stable at high temperatures. When chemical derivatives of these fullerenes are formed, the helium stays inside.[118] If helium-3 is used, it can be readily observed by helium nuclear magnetic resonance spectroscopy.[119] Many fullerenes containing helium-3 have been reported. Although the helium atoms are not attached by covalent or ionic bonds, these substances have distinct properties and a definite composition, like all stoichiometric chemical compounds.

Under high pressures helium can form compounds with various other elements. Helium-nitrogen clathrate (He(N2)11) crystals have been grown at room temperature at pressures ca. 10 GPa in a diamond anvil cell.[120] The insulating electride Na2He has been shown to be thermodynamically stable at pressures above 113 GPa. It has a fluorite structure.[121]

Occurrence and production

Natural abundance

Although it is rare on Earth, helium is the second most abundant element in the known Universe, constituting 23% of its baryonic mass. Only hydrogen is more abundant.[25] The vast majority of helium was formed by Big Bang nucleosynthesis one to three minutes after the Big Bang. As such, measurements of its abundance contribute to cosmological models. In stars, it is formed by the nuclear fusion of hydrogen in proton–proton chain reactions and the CNO cycle, part of stellar nucleosynthesis.[103]

In the Earth's atmosphere, the concentration of helium by volume is only 5.2 parts per million.[122][123] The concentration is low and fairly constant despite the continuous production of new helium because most helium in the Earth's atmosphere escapes into space by several processes.[124][125][126] In the Earth's heterosphere, a part of the upper atmosphere, helium and other lighter gases are the most abundant elements.

Most helium on Earth is a result of radioactive decay. Helium is found in large amounts in minerals of uranium and thorium, including uraninite and its varieties cleveite and pitchblende,[17][127] carnotite and monazite (a group name; "monazite" usually refers to monazite-(Ce)),[128][129] because they emit alpha particles (helium nuclei, He2+) to which electrons immediately combine as soon as the particle is stopped by the rock. In this way an estimated 3000 metric tons of helium are generated per year throughout the lithosphere.[130][131][132] In the Earth's crust, the concentration of helium is 8 parts per billion. In seawater, the concentration is only 4 parts per trillion. There are also small amounts in mineral springs, volcanic gas, and meteoric iron. Because helium is trapped in the subsurface under conditions that also trap natural gas, the greatest natural concentrations of helium on the planet are found in natural gas, from which most commercial helium is extracted. The concentration varies in a broad range from a few ppm to more than 7% in a small gas field in San Juan County, New Mexico.[133][134]

As of 2021 the world's helium reserves were estimated at 31 billion cubic meters, with a third of that being in Qatar.[135] In 2015 and 2016 additional probable reserves were announced to be under the Rocky Mountains in North America[136] and in the East African Rift.[137]

Modern extraction and distribution

For large-scale use, helium is extracted by fractional distillation from natural gas, which can contain as much as 7% helium.[138] Since helium has a lower boiling point than any other element, low temperature and high pressure are used to liquefy nearly all the other gases (mostly nitrogen and methane). The resulting crude helium gas is purified by successive exposures to lowering temperatures, in which almost all of the remaining nitrogen and other gases are precipitated out of the gaseous mixture. Activated charcoal is used as a final purification step, usually resulting in 99.995% pure Grade-A helium.[27] The principal impurity in Grade-A helium is neon. In a final production step, most of the helium that is produced is liquefied via a cryogenic process. This is necessary for applications requiring liquid helium and also allows helium suppliers to reduce the cost of long-distance transportation, as the largest liquid helium containers have more than five times the capacity of the largest gaseous helium tube trailers.[76][139]

In 2008, approximately 169 million standard cubic meters (SCM) of helium were extracted from natural gas or withdrawn from helium reserves with approximately 78% from the United States, 10% from Algeria, and most of the remainder from Russia, Poland and Qatar.[140] By 2013, increases in helium production in Qatar (under the company Qatargas managed by Air Liquide) had increased Qatar's fraction of world helium production to 25%, and made it the second largest exporter after the United States.[141] An estimated 54 billion cubic feet (1.5×109 m3) deposit of helium was found in Tanzania in 2016.[142] A large-scale helium plant was opened in Ningxia, China in 2020.[143]

In the United States, most helium is extracted from natural gas of the Hugoton and nearby gas fields in Kansas, Oklahoma, and the Panhandle Field in Texas.[76][144] Much of this gas was once sent by pipeline to the National Helium Reserve, but since 2005 this reserve is being depleted and sold off, and is expected to be largely depleted by 2021,[141] under the October 2013 Responsible Helium Administration and Stewardship Act (H.R. 527).[145]

Diffusion of crude natural gas through special semipermeable membranes and other barriers is another method to recover and purify helium.[146] In 1996, the U.S. had proven helium reserves, in such gas well complexes, of about 147 billion standard cubic feet (4.2 billion SCM).[147] At rates of use at that time (72 million SCM per year in the U.S.; see pie chart below) this would have been enough helium for about 58 years of U.S. use, and less than this (perhaps 80% of the time) at world use rates, although factors in saving and processing impact effective reserve numbers.

Helium must be extracted from natural gas because it is present in air at only a fraction of that of neon, yet the demand for it is far higher. It is estimated that if all neon production were retooled to save helium, 0.1% of the world's helium demands would be satisfied. Similarly, only 1% of the world's helium demands could be satisfied by re-tooling all air distillation plants.[148] Helium can be synthesized by bombardment of lithium or boron with high-velocity protons, or by bombardment of lithium with deuterons, but these processes are a completely uneconomical method of production.[149]

Helium is commercially available in either liquid or gaseous form. As a liquid, it can be supplied in small insulated containers called dewars which hold as much as 1,000 liters of helium, or in large ISO containers which have nominal capacities as large as 42 m3 (around 11,000 U.S. gallons). In gaseous form, small quantities of helium are supplied in high-pressure cylinders holding as much as 8 m3 (approx. 282 standard cubic feet), while large quantities of high-pressure gas are supplied in tube trailers which have capacities of as much as 4,860 m3 (approx. 172,000 standard cubic feet).

Conservation advocates

Main article: Helium storage and conservation

According to helium conservationists like Nobel laureate physicist Robert Coleman Richardson, writing in 2010, the free market price of helium has contributed to "wasteful" usage (e.g. for helium balloons). Prices in the 2000s had been lowered by the decision of the U.S. Congress to sell off the country's large helium stockpile by 2015.[150] According to Richardson, the price needed to be multiplied by 20 to eliminate the excessive wasting of helium. In the paper Stop squandering helium published in 2012, it was also proposed to create an International Helium Agency that would build a sustainable market for "this precious commodity".[151]

Applications

 
The largest single use of liquid helium is to cool the superconducting magnets in modern MRI scanners.

Estimated 2014 U.S. fractional helium use by category. Total use is 34 million cubic meters.[152]

  Cryogenics (32%)
  Pressurizing and purging (18%)
  Welding (13%)
  Controlled atmospheres (18%)
  Leak detection (4%)
  Breathing mixtures (2%)
  Other (13%)

While balloons are perhaps the best known use of helium, they are a minor part of all helium use.[71] Helium is used for many purposes that require some of its unique properties, such as its low boiling point, low density, low solubility, high thermal conductivity, or inertness. Of the 2014 world helium total production of about 32 million kg (180 million standard cubic meters) helium per year, the largest use (about 32% of the total in 2014) is in cryogenic applications, most of which involves cooling the superconducting magnets in medical MRI scanners and NMR spectrometers.[153] Other major uses were pressurizing and purging systems, welding, maintenance of controlled atmospheres, and leak detection. Other uses by category were relatively minor fractions.[152]

Controlled atmospheres

Helium is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, and in gas chromatography,[92] because it is inert. Because of its inertness, thermally and calorically perfect nature, high speed of sound, and high value of the heat capacity ratio, it is also useful in supersonic wind tunnels[154] and impulse facilities.[155]

Gas tungsten arc welding

Main article: Gas tungsten arc welding

Helium is used as a shielding gas in arc welding processes on materials that at welding temperatures are contaminated and weakened by air or nitrogen.[25] A number of inert shielding gases are used in gas tungsten arc welding, but helium is used instead of cheaper argon especially for welding materials that have higher heat conductivity, like aluminium or copper.

Minor uses

Industrial leak detection

 
A dual chamber helium leak detection machine

One industrial application for helium is leak detection. Because helium diffuses through solids three times faster than air, it is used as a tracer gas to detect leaks in high-vacuum equipment (such as cryogenic tanks) and high-pressure containers.[156] The tested object is placed in a chamber, which is then evacuated and filled with helium. The helium that escapes through the leaks is detected by a sensitive device (helium mass spectrometer), even at the leak rates as small as 10−9 mbar·L/s (10−10 Pa·m3/s). The measurement procedure is normally automatic and is called helium integral test. A simpler procedure is to fill the tested object with helium and to manually search for leaks with a hand-held device.[157]

Helium leaks through cracks should not be confused with gas permeation through a bulk material. While helium has documented permeation constants (thus a calculable permeation rate) through glasses, ceramics, and synthetic materials, inert gases such as helium will not permeate most bulk metals.[158]

Flight

 
Because of its low density and incombustibility, helium is the gas of choice to fill airships such as the Goodyear blimp.

Because it is lighter than air, airships and balloons are inflated with helium for lift. While hydrogen gas is more buoyant, and escapes permeating through a membrane at a lower rate, helium has the advantage of being non-flammable, and indeed fire-retardant. Another minor use is in rocketry, where helium is used as an ullage medium to backfill rocket propellant tanks in flight and to condense hydrogen and oxygen to make rocket fuel. It is also used to purge fuel and oxidizer from ground support equipment prior to launch and to pre-cool liquid hydrogen in space vehicles. For example, the Saturn V rocket used in the Apollo program needed about 370,000 m3 (13 million cubic feet) of helium to launch.[92]

Minor commercial and recreational uses

Helium as a breathing gas has no narcotic properties, so helium mixtures such as trimix, heliox and heliair are used for deep diving to reduce the effects of narcosis, which worsen with increasing depth.[159][160] As pressure increases with depth, the density of the breathing gas also increases, and the low molecular weight of helium is found to considerably reduce the effort of breathing by lowering the density of the mixture. This reduces the Reynolds number of flow, leading to a reduction of turbulent flow and an increase in laminar flow, which requires less work of breathing.[161][162] At depths below 150 metres (490 ft) divers breathing helium–oxygen mixtures begin to experience tremors and a decrease in psychomotor function, symptoms of high-pressure nervous syndrome.[163] This effect may be countered to some extent by adding an amount of narcotic gas such as hydrogen or nitrogen to a helium–oxygen mixture.[164]

Helium–neon lasers, a type of low-powered gas laser producing a red beam, had various practical applications which included barcode readers and laser pointers, before they were almost universally replaced by cheaper diode lasers.[25]

For its inertness and high thermal conductivity, neutron transparency, and because it does not form radioactive isotopes under reactor conditions, helium is used as a heat-transfer medium in some gas-cooled nuclear reactors.[156]

Helium, mixed with a heavier gas such as xenon, is useful for thermoacoustic refrigeration due to the resulting high heat capacity ratio and low Prandtl number.[165] The inertness of helium has environmental advantages over conventional refrigeration systems which contribute to ozone depletion or global warming.[166]

Helium is also used in some hard disk drives.[167]

Scientific uses

The use of helium reduces the distorting effects of temperature variations in the space between lenses in some telescopes, due to its extremely low index of refraction.[27] This method is especially used in solar telescopes where a vacuum tight telescope tube would be too heavy.[168][169]

Helium is a commonly used carrier gas for gas chromatography.

The age of rocks and minerals that contain uranium and thorium can be estimated by measuring the level of helium with a process known as helium dating.[25][27]

Helium at low temperatures is used in cryogenics, and in certain cryogenics applications. As examples of applications, liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity, such as in superconducting magnets for magnetic resonance imaging. The Large Hadron Collider at CERN uses 96 metric tons of liquid helium to maintain the temperature at 1.9 K (−271.25 °C; −456.25 °F).[170]

Medical uses

Helium was approved for medical use in the United States in April 2020 for humans and animals.[171][172]

As a contaminant

While chemically inert, helium contamination impairs the operation of microelectromechanical systems (MEMS) such that iPhones may fail.[173]

Inhalation and safety

Effects

Neutral helium at standard conditions is non-toxic, plays no biological role and is found in trace amounts in human blood.

 
Effect of helium on a human voice
The effect of helium on a human voice
Problems playing this file? See media help.

The speed of sound in helium is nearly three times the speed of sound in air. Because the natural resonance frequency of a gas-filled cavity is proportional to the speed of sound in the gas, when helium is inhaled, a corresponding increase occurs in the resonant frequencies of the vocal tract, which is the amplifier of vocal sound.[25][174] This increase in the resonant frequency of the amplifier (the vocal tract) gives an increased amplification to the high-frequency components of the sound wave produced by the direct vibration of the vocal folds, compared to the case when the voice box is filled with air. When a person speaks after inhaling helium gas, the muscles that control the voice box still move in the same way as when the voice box is filled with air, therefore the fundamental frequency (sometimes called pitch) produced by direct vibration of the vocal folds does not change.[175] However, the high-frequency-preferred amplification causes a change in timbre of the amplified sound, resulting in a reedy, duck-like vocal quality. The opposite effect, lowering resonant frequencies, can be obtained by inhaling a dense gas such as sulfur hexafluoride or xenon.

Hazards

Inhaling helium can be dangerous if done to excess, since helium is a simple asphyxiant and so displaces oxygen needed for normal respiration.[25][176] Fatalities have been recorded, including a youth who suffocated in Vancouver in 2003 and two adults who suffocated in South Florida in 2006.[177][178] In 1998, an Australian girl from Victoria fell unconscious and temporarily turned blue after inhaling the entire contents of a party balloon.[179][180][181] Inhaling helium directly from pressurized cylinders or even balloon filling valves is extremely dangerous, as high flow rate and pressure can result in barotrauma, fatally rupturing lung tissue.[176][182]

Death caused by helium is rare. The first media-recorded case was that of a 15-year-old girl from Texas who died in 1998 from helium inhalation at a friend's party; the exact type of helium death is unidentified.[179][180][181]

In the United States only two fatalities were reported between 2000 and 2004, including a man who died in North Carolina of barotrauma in 2002.[177][182] A youth asphyxiated in Vancouver during 2003, and a 27-year-old man in Australia had an embolism after breathing from a cylinder in 2000.[177] Since then two adults asphyxiated in South Florida in 2006,[177][178][183] and there were cases in 2009 and 2010, one a Californian youth who was found with a bag over his head, attached to a helium tank,[184] and another teenager in Northern Ireland died of asphyxiation.[185] At Eagle Point, Oregon a teenage girl died in 2012 from barotrauma at a party.[186][187][188] A girl from Michigan died from hypoxia later in the year.[189]

On February 4, 2015, it was revealed that, during the recording of their main TV show on January 28, a 12-year-old member (name withheld) of Japanese all-girl singing group 3B Junior suffered from air embolism, losing consciousness and falling into a coma as a result of air bubbles blocking the flow of blood to the brain, after inhaling huge quantities of helium as part of a game. The incident was not made public until a week later.[190][191] The staff of TV Asahi held an emergency press conference to communicate that the member had been taken to the hospital and is showing signs of rehabilitation such as moving eyes and limbs, but her consciousness has not yet been sufficiently recovered. Police have launched an investigation due to a neglect of safety measures.[192][193]

The safety issues for cryogenic helium are similar to those of liquid nitrogen; its extremely low temperatures can result in cold burns, and the liquid-to-gas expansion ratio can cause explosions if no pressure-relief devices are installed. Containers of helium gas at 5 to 10 K should be handled as if they contain liquid helium due to the rapid and significant thermal expansion that occurs when helium gas at less than 10 K is warmed to room temperature.[92]

At high pressures (more than about 20 atm or two MPa), a mixture of helium and oxygen (heliox) can lead to high-pressure nervous syndrome, a sort of reverse-anesthetic effect; adding a small amount of nitrogen to the mixture can alleviate the problem.[194][163]

See also

Notes

  1. ^ A few authors dispute the placement of helium in the noble gas column, preferring to place it above beryllium with the alkaline earth metals. They do so on the grounds of helium's 1s2 electron configuration, which is analogous to the ns2 valence configurations of the alkaline earth metals, and furthermore point to some specific trends that are more regular with helium over beryllium.[6][7][8][9][10] However, the classification of helium with the other noble gases remains near-universal, as its extraordinary inertness is extremely close to that of the other light noble gases neon and argon.[11]

References

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  2. ^ Shuen-Chen Hwang, Robert D. Lein, Daniel A. Morgan (2005). "Noble Gases". Kirk Othmer Encyclopedia of Chemical Technology. Wiley. pp. 343–383. doi:10.1002/0471238961.0701190508230114.a01.
  3. ^ Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
  4. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
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  6. ^ Grochala, Wojciech (1 November 2017). "On the position of helium and neon in the Periodic Table of Elements". Foundations of Chemistry. 20 (2018): 191–207. doi:10.1007/s10698-017-9302-7.
  7. ^ Bent Weberg, Libby (18 January 2019). ""The" periodic table". Chemical & Engineering News. 97 (3). Retrieved 27 March 2020.
  8. ^ Grandinetti, Felice (23 April 2013). "Neon behind the signs". Nature Chemistry. 5 (2013): 438. Bibcode:2013NatCh...5..438G. doi:10.1038/nchem.1631. PMID 23609097.
  9. ^ Kurushkin, Mikhail (2020). "Helium's placement in the Periodic Table from a crystal structure viewpoint". IUCrJ. 7 (4): 577–578. doi:10.1107/S2052252520007769. PMC 7340260. PMID 32695406. Retrieved 19 June 2020.
  10. ^ Labarca, Martín; Srivaths, Akash (2016). . Bulgarian Journal of Science Education. 25 (4): 514–530. Archived from the original on 29 November 2021. Retrieved 19 June 2020.
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  12. ^ Rayet, G. (1868) (Spectral analysis of the protuberances observed during the total solar eclipse, seen on 18 August 1868, from the Malacca peninsula), Comptes rendus ... , 67 : 757–759. From p. 758: " ... je vis immédiatement une série de neuf lignes brillantes qui ... me semblent devoir être assimilées aux lignes principales du spectre solaire, B, D, E, b, une ligne inconnue, F, et deux lignes du groupe G." ( ... I saw immediately a series of nine bright lines that ... seemed to me should be classed as the principal lines of the solar spectrum, B, D, E, b, an unknown line, F, and two lines of the group G.)
  13. ^ Captain C. T. Haig (1868) "Account of spectroscopic observations of the eclipse of the sun, August 18th, 1868" Proceedings of the Royal Society of London, 17 : 74–80. From p. 74: "I may state at once that I observed the spectra of two red flames close to each other, and in their spectra two broad bright bands quite sharply defined, one rose-madder and the other light golden."
  14. ^ Pogson filed his observations of the 1868 eclipse with the local Indian government, but his report wasn't published. (Biman B. Nath, The Story of Helium and the Birth of Astrophysics (New York, New York: Springer, 2013), p. 8.) Nevertheless, Lockyer quoted from his report. From p. 320 17 August 2018 at the Wayback Machine of Lockyer, J. Norman (1896) "The story of helium. Prologue," Nature, 53 : 319–322 : "Pogson, in referring to the eclipse of 1868, said that the yellow line was "at D, or near D." "
  15. ^ Lieutenant John Herschel (1868) "Account of the solar eclipse of 1868, as seen at Jamkandi in the Bombay Presidency," Proceedings of the Royal Society of London, 17 : 104–120. From p. 113: As the moment of the total solar eclipse approached, " … I recorded an increasing brilliancy in the spectrum in the neighborhood of D, so great in fact as to prevent any measurement of that line till an opportune cloud moderated the light. I am not prepared to offer any explanation of this." From p. 117: "I also consider that there can be no question that the ORANGE LINE was identical with D, so far as the capacity of the instrument to establish any such identity is concerned."
  16. ^ In his initial report to the French Academy of Sciences about the 1868 eclipse, Janssen made no mention of a yellow line in the solar spectrum. See:
    • Janssen (1868) "Indication de quelques-uns des résultats obtenus à Cocanada, pendant l'éclipse du mois d'août dernier, et à la suite de cette éclipse" (Information on some of the results obtained at Cocanada, during the eclipse of the month of last August, and following that eclipse), Comptes rendus ... , 67 : 838–839.
    • Wheeler M. Sears, Helium: The Disappearing Element (Heidelberg, Germany: Springer, 2015), p. 44.
    • Françoise Launay with Storm Dunlop, trans., The Astronomer Jules Janssen: A Globetrotter of Celestial Physics (Heidelberg, Germany: Springer, 2012), p. 45.
    However, subsequently, in an unpublished letter of 19 December 1868 to Charles Sainte-Claire Deville, Janssen asked Deville to inform the French Academy of Sciences that : "Several observers have claimed the bright D line as forming part of the spectrum of the prominences on 18 August. The bright yellow line did indeed lie very close to D, but the light was more refrangible [i.e., of shorter wavelength] than those of the D lines. My subsequent studies of the Sun have shown the accuracy of what I state here." (See: (Launay, 2012), p. 45.)
  17. ^ a b "Cleveite". Mindat.org. Retrieved 14 February 2020.
  18. ^ "Uraninite". Mindat.org. Retrieved 14 February 2020.
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  21. ^ Siegel, Ethan (12 December 2012). "Why the World Will Run Out of Helium". Starts with a Bang. Scienceblogs.com. from the original on 14 September 2013. Retrieved 16 September 2013.
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  25. ^ a b c d e f g h i j k l Emsley, John (2001). Nature's Building Blocks. Oxford: Oxford University Press. pp. 175–179. ISBN 978-0-19-850341-5.
  26. ^ Lockyer, J. N. (October 1868). "Notice of an observation of the spectrum of a solar prominence". Proceedings of the Royal Society of London. 17: 91–92. Bibcode:1868RSPS...17...91L. doi:10.1098/rspl.1868.0011. JSTOR 112357. S2CID 163097539. Retrieved 3 June 2018.
  27. ^ a b c d e f g h i j k l m n o p q r s t u v w Hampel, Clifford A. (1968). The Encyclopedia of the Chemical Elements. New York: Van Nostrand Reinhold. pp. 256–268. ISBN 978-0-442-15598-8.
  28. ^ Harper, Douglas. "helium". Online Etymology Dictionary.
  29. ^ Thomson, William (August 3, 1871). "Inaugural Address of Sir William Thomson". Nature. 4 (92): 261–278 [268]. Bibcode:1871Natur...4..261.. doi:10.1038/004261a0. PMC 2070380. from the original on December 2, 2016. Retrieved February 22, 2016. Frankland and Lockyer find the yellow prominences to give a very decided bright line not far from D, but hitherto not identified with any terrestrial flame. It seems to indicate a new substance, which they propose to call Helium
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Bibliography

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  • Committee on the Impact of Selling the Federal Helium Reserve; Commission on Physical Sciences, Mathematics, and Applications; Commission on Engineering and Technical Systems; National Research Council (2000). The Impact of Selling the Federal Helium Reserve. The National Academies Press. ISBN 978-0-309-07038-6. Retrieved 2010-04-02.
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  • Vercheval, J. (2003). . Belgian Institute for Space Aeronomy. Archived from the original on 2005-01-01. Retrieved 2008-07-12.

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General

  • With some history of helium.
  • U.S. Geological Survey publications on helium beginning 1996: Helium
  • Aga website
  • It's Elemental – Helium
  • Chemistry in its element podcast (MP3) from the Royal Society of Chemistry's Chemistry World: Helium
  • ; includes health and safety information regarding accidental exposures to helium

More detail

  • Helium at The Periodic Table of Videos (University of Nottingham)
  • Helium at the Helsinki University of Technology; includes pressure-temperature phase diagrams for helium-3 and helium-4
  • Lancaster University, Ultra Low Temperature Physics – includes a summary of some low temperature techniques
  • Video: Demonstration of superfluid helium (Alfred Leitner, 1963, 38 min.)

Miscellaneous

  • with audio samples that demonstrate the unchanged voice pitch

Helium shortage

  • America's Helium Supply: Options for Producing More Helium from Federal Land: Oversight Hearing before the Subcommittee on Energy and Mineral Resources of the Committee on Natural Resources, U.S. House Of Representatives, One Hundred Thirteenth Congress, First Session, Thursday, July 11, 2013
  • Helium Program: Urgent Issues Facing BLM's Storage and Sale of Helium Reserves: Testimony before the Committee on Natural Resources, House of Representatives Government Accountability Office
  • Kramer, David (May 22, 2012). . Archived from the original on October 27, 2012.
  • Richardson, Robert C.; Chan, Moses (2009). (PDF). Archived from the original (PDF) on 2015-06-14.

May 11, 2023
helium, this, article, about, chemical, element, other, uses, disambiguation, from, greek, ἥλιος, romanized, helios, chemical, element, with, symbol, atomic, number, colorless, odorless, tasteless, toxic, inert, monatomic, first, noble, group, periodic, table,. This article is about the chemical element For other uses see Helium disambiguation Helium from Greek ἥlios romanized helios lit sun is a chemical element with the symbol He and atomic number 2 It is a colorless odorless tasteless non toxic inert monatomic gas and the first in the noble gas group in the periodic table a Its boiling point is the lowest among all the elements and it does not have a melting point at standard pressure It is the second lightest and second most abundant element in the observable universe after hydrogen It is present at about 24 of the total elemental mass which is more than 12 times the mass of all the heavier elements combined Its abundance is similar to this in both the Sun and in Jupiter due to the very high nuclear binding energy per nucleon of helium 4 with respect to the next three elements after helium This helium 4 binding energy also accounts for why it is a product of both nuclear fusion and radioactive decay The most common isotope of helium in the universe is helium 4 the vast majority of which was formed during the Big Bang Large amounts of new helium are created by nuclear fusion of hydrogen in stars Helium 2HeHeliumPronunciation ˈ h iː l i e m wbr HEE lee em Appearancecolorless gas exhibiting a gray cloudy glow or reddish orange if an especially high voltage is used when placed in an electric fieldStandard atomic weight Ar He 4 002602 0 0000024 0026 0 0001 abridged 1 Helium in the periodic tableHydrogen HeliumLithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine NeonSodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine ArgonPotassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine KryptonRubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine XenonCaesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury element Thallium Lead Bismuth Polonium Astatine RadonFrancium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson He Nehydrogen helium lithiumAtomic number Z 2Groupgroup 18 noble gases Periodperiod 1Block s blockElectron configuration1s2Electrons per shell2Physical propertiesPhase at STPgasMelting point0 95 K 272 20 C 457 96 F at 2 5 MPa Boiling point4 222 K 268 928 C 452 070 F Density at STP 0 1786 g Lwhen liquid at m p 0 145 g cm3when liquid at b p 0 125 g cm3Triple point2 177 K 5 043 kPaCritical point5 1953 K 0 22746 MPaHeat of fusion0 0138 kJ molHeat of vaporization0 0829 kJ molMolar heat capacity20 78 J mol K 2 Vapor pressure defined by ITS 90 P Pa 1 10 100 1 k 10 k 100 kat T K 1 23 1 67 2 48 4 21Atomic propertiesOxidation states0ElectronegativityPauling scale no dataIonization energies1st 2372 3 kJ mol2nd 5250 5 kJ molCovalent radius28 pmVan der Waals radius140 pmSpectral lines of heliumOther propertiesNatural occurrenceprimordialCrystal structure hexagonal close packed hcp Speed of sound972 m sThermal conductivity0 1513 W m K Magnetic orderingdiamagnetic 3 Molar magnetic susceptibility 1 88 10 6 cm3 mol 298 K 4 CAS Number7440 59 7HistoryNamingafter Helios Greek god of the SunDiscoveryPierre Janssen Norman Lockyer 1868 First isolationWilliam Ramsay Per Teodor Cleve Abraham Langlet 1895 Isotopes of heliumveMain isotopes 5 Decayabun dance half life t1 2 mode pro duct3He 0 0002 stable4He 99 9998 stable Category Heliumviewtalkedit referencesHelium was first detected as an unknown yellow spectral line signature in sunlight during a solar eclipse in 1868 by Georges Rayet 12 Captain C T Haig 13 Norman R Pogson 14 and Lieutenant John Herschel 15 and was subsequently confirmed by French astronomer Jules Janssen 16 Janssen is often jointly credited with detecting the element along with Norman Lockyer Janssen recorded the helium spectral line during the solar eclipse of 1868 while Lockyer observed it from Britain Lockyer was the first to propose that the line was due to a new element which he named after the sun The formal discovery of the element was made in 1895 by chemists Sir William Ramsay Per Teodor Cleve and Nils Abraham Langlet who found helium emanating from the uranium ore cleveite which is now not regarded as a separate mineral species but as a variety of uraninite 17 18 In 1903 large reserves of helium were found in natural gas fields in parts of the United States by far the largest supplier of the gas today Liquid helium is used in cryogenics its largest single use consuming about a quarter of production and in the cooling of superconducting magnets with its main commercial application in MRI scanners Helium s other industrial uses as a pressurizing and purge gas as a protective atmosphere for arc welding and in processes such as growing crystal to make silicon wafers account for half of the gas produced A small but well known use is as a lifting gas in balloons and airships 19 As with any gas whose density differs from that of air inhaling a small volume of helium temporarily changes the timbre and quality of the human voice In scientific research the behavior of the two fluid phases of helium 4 helium I and helium II is important to researchers studying quantum mechanics in particular the property of superfluidity and to those looking at the phenomena such as superconductivity produced in matter near absolute zero On Earth it is relatively rare 5 2 ppm by volume in the atmosphere Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements thorium and uranium although there are other examples as the alpha particles emitted by such decays consist of helium 4 nuclei This radiogenic helium is trapped with natural gas in concentrations as great as 7 by volume from which it is extracted commercially by a low temperature separation process called fractional distillation Terrestrial helium is a non renewable resource because once released into the atmosphere it promptly escapes into space Its supply is thought to be rapidly diminishing 20 21 However some studies suggest that helium produced deep in the earth by radioactive decay can collect in natural gas reserves in larger than expected quantities 22 in some cases having been released by volcanic activity 23 Contents 1 History 1 1 Scientific discoveries 1 2 Extraction and use 2 Characteristics 2 1 Atom 2 1 1 In quantum mechanics 2 1 2 Related stability of the helium 4 nucleus and electron shell 2 2 Gas and plasma phases 2 3 Liquid phase 2 3 1 Helium I 2 3 2 Helium II 2 4 Isotopes 2 5 Properties 3 Compounds 4 Occurrence and production 4 1 Natural abundance 4 2 Modern extraction and distribution 4 3 Conservation advocates 5 Applications 5 1 Controlled atmospheres 5 2 Gas tungsten arc welding 5 3 Minor uses 5 3 1 Industrial leak detection 5 3 2 Flight 5 3 3 Minor commercial and recreational uses 5 3 4 Scientific uses 5 3 5 Medical uses 6 As a contaminant 7 Inhalation and safety 7 1 Effects 7 2 Hazards 8 See also 9 Notes 10 References 11 Bibliography 12 External linksHistoryScientific discoveries The first evidence of helium was observed on August 18 1868 as a bright yellow line with a wavelength of 587 49 nanometers in the spectrum of the chromosphere of the Sun The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur India 24 25 This line was initially assumed to be sodium On October 20 of the same year English astronomer Norman Lockyer observed a yellow line in the solar spectrum which he named the D3 because it was near the known D1 and D2 Fraunhofer line lines of sodium 26 27 He concluded that it was caused by an element in the Sun unknown on Earth Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun ἥlios helios 28 29 Spectral lines of helium In 1881 Italian physicist Luigi Palmieri detected helium on Earth for the first time through its D3 spectral line when he analyzed a material that had been sublimated during a recent eruption of Mount Vesuvius 30 Sir William Ramsay the discoverer of terrestrial helium The cleveite sample from which Ramsay first purified helium 31 On March 26 1895 Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite a variety of uraninite with at least 10 rare earth elements with mineral acids Ramsay was looking for argon but after separating nitrogen and oxygen from the gas liberated by sulfuric acid he noticed a bright yellow line that matched the D3 line observed in the spectrum of the Sun 27 32 33 34 These samples were identified as helium by Lockyer and British physicist William Crookes 35 36 It was independently isolated from cleveite in the same year by chemists Per Teodor Cleve and Abraham Langlet in Uppsala Sweden who collected enough of the gas to accurately determine its atomic weight 37 38 25 39 Helium was also isolated by the American geochemist William Francis Hillebrand prior to Ramsay s discovery when he noticed unusual spectral lines while testing a sample of the mineral uraninite Hillebrand however attributed the lines to nitrogen 40 His letter of congratulations to Ramsay offers an interesting case of discovery and near discovery in science 41 In 1907 Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei by allowing the particles to penetrate the thin glass wall of an evacuated tube then creating a discharge in the tube to study the spectrum of the new gas inside 42 In 1908 helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than 5 K 268 15 C 450 67 F 43 44 He tried to solidify it by further reducing the temperature but failed because helium does not solidify at atmospheric pressure Onnes student Willem Hendrik Keesom was eventually able to solidify 1 cm3 of helium in 1926 by applying additional external pressure 45 46 In 1913 Niels Bohr published his trilogy 47 48 on atomic structure that included a reconsideration of the Pickering Fowler series as central evidence in support of his model of the atom 49 50 This series is named for Edward Charles Pickering who in 1896 published observations of previously unknown lines in the spectrum of the star z Puppis 51 these are now known to occur with Wolf Rayet and other hot stars 52 Pickering attributed the observation lines at 4551 5411 and 10123 A to a new form of hydrogen with half integer transition levels 53 54 In 1912 Alfred Fowler 55 managed to produce similar lines from a hydrogen helium mixture and supported Pickering s conclusion as to their origin 56 Bohr s model does not allow for half integer transitions nor does quantum mechanics and Bohr concluded that Pickering and Fowler were wrong and instead assigned these spectral lines to ionised helium He 57 Fowler was initially skeptical 58 but was ultimately convinced 59 that Bohr was correct 47 and by 1915 spectroscopists had transferred the Pickering Fowler series definitively from hydrogen to helium 50 60 Bohr s theoretical work on the Pickering series had demonstrated the need for a re examination of problems that seemed already to have been solved within classical theories and provided important confirmation for his atomic theory 50 In 1938 Russian physicist Pyotr Leonidovich Kapitsa discovered that helium 4 has almost no viscosity at temperatures near absolute zero a phenomenon now called superfluidity 61 This phenomenon is related to Bose Einstein condensation In 1972 the same phenomenon was observed in helium 3 but at temperatures much closer to absolute zero by American physicists Douglas D Osheroff David M Lee and Robert C Richardson The phenomenon in helium 3 is thought to be related to pairing of helium 3 fermions to make bosons in analogy to Cooper pairs of electrons producing superconductivity 62 Extraction and use Historical marker denoting a massive helium find near Dexter Kansas The examples and perspective in this section may not represent a worldwide view of the subject You may improve this section discuss the issue on the talk page or create a new section as appropriate February 2022 Learn how and when to remove this template message After an oil drilling operation in 1903 in Dexter Kansas produced a gas geyser that would not burn Kansas state geologist Erasmus Haworth collected samples of the escaping gas and took them back to the University of Kansas at Lawrence where with the help of chemists Hamilton Cady and David McFarland he discovered that the gas consisted of by volume 72 nitrogen 15 methane a combustible percentage only with sufficient oxygen 1 hydrogen and 12 an unidentifiable gas 25 63 With further analysis Cady and McFarland discovered that 1 84 of the gas sample was helium 64 65 This showed that despite its overall rarity on Earth helium was concentrated in large quantities under the American Great Plains available for extraction as a byproduct of natural gas 66 This enabled the United States to become the world s leading supplier of helium Following a suggestion by Sir Richard Threlfall the United States Navy sponsored three small experimental helium plants during World War I The goal was to supply barrage balloons with the non flammable lighter than air gas A total of 5 700 m3 200 000 cu ft of 92 helium was produced in the program even though less than a cubic meter of the gas had previously been obtained 27 Some of this gas was used in the world s first helium filled airship the U S Navy s C class blimp C 7 which flew its maiden voyage from Hampton Roads Virginia to Bolling Field in Washington D C on December 1 1921 67 nearly two years before the Navy s first rigid helium filled airship the Naval Aircraft Factory built USS Shenandoah flew in September 1923 Although the extraction process using low temperature gas liquefaction was not developed in time to be significant during World War I production continued Helium was primarily used as a lifting gas in lighter than air craft During World War II the demand increased for helium for lifting gas and for shielded arc welding The helium mass spectrometer was also vital in the atomic bomb Manhattan Project 68 The government of the United States set up the National Helium Reserve in 1925 at Amarillo Texas with the goal of supplying military airships in time of war and commercial airships in peacetime 27 Because of the Helium Act of 1925 which banned the export of scarce helium on which the US then had a production monopoly together with the prohibitive cost of the gas German Zeppelins was forced to use hydrogen as lifting gas which would gain infamy in the Hindenburg disaster The helium market after World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen hydrogen rocket fuel among other uses during the Space Race and Cold War Helium use in the United States in 1965 was more than eight times the peak wartime consumption 69 After the Helium Acts Amendments of 1960 Public Law 86 777 the U S Bureau of Mines arranged for five private plants to recover helium from natural gas For this helium conservation program the Bureau built a 425 mile 684 km pipeline from Bushton Kansas to connect those plants with the government s partially depleted Cliffside gas field near Amarillo Texas This helium nitrogen mixture was injected and stored in the Cliffside gas field until needed at which time it was further purified 70 By 1995 a billion cubic meters of the gas had been collected and the reserve was US 1 4 billion in debt prompting the Congress of the United States in 1996 to discontinue the reserve 25 71 The resulting Helium Privatization Act of 1996 72 Public Law 104 273 directed the United States Department of the Interior to empty the reserve with sales starting by 2005 73 Helium produced between 1930 and 1945 was about 98 3 pure 2 nitrogen which was adequate for airships In 1945 a small amount of 99 9 helium was produced for welding use By 1949 commercial quantities of Grade A 99 95 helium were available 74 For many years the United States produced more than 90 of commercially usable helium in the world while extraction plants in Canada Poland Russia and other nations produced the remainder In the mid 1990s a new plant in Arzew Algeria producing 17 million cubic meters 600 million cubic feet began operation with enough production to cover all of Europe s demand Meanwhile by 2000 the consumption of helium within the U S had risen to more than 15 million kg per year 75 In 2004 2006 additional plants in Ras Laffan Qatar and Skikda Algeria were built Algeria quickly became the second leading producer of helium 76 Through this time both helium consumption and the costs of producing helium increased 77 From 2002 to 2007 helium prices doubled 78 As of 2012 update the United States National Helium Reserve accounted for 30 percent of the world s helium 79 The reserve was expected to run out of helium in 2018 79 Despite that a proposed bill in the United States Senate would allow the reserve to continue to sell the gas Other large reserves were in the Hugoton in Kansas United States and nearby gas fields of Kansas and the panhandles of Texas and Oklahoma New helium plants were scheduled to open in 2012 in Qatar Russia and the US state of Wyoming but they were not expected to ease the shortage 79 In 2013 Qatar started up the world s largest helium unit 80 although the 2017 Qatar diplomatic crisis severely affected helium production there 81 2014 was widely acknowledged to be a year of over supply in the helium business following years of renowned shortages 82 Nasdaq reported 2015 that for Air Products an international corporation that sells gases for industrial use helium volumes remain under economic pressure due to feedstock supply constraints 83 Also see the sub section Conservation advocates in this article s section Occurrence and production below CharacteristicsAtom Main article Helium atom This section needs additional citations for verification Please help improve this article by adding citations to reliable sources in this section Unsourced material may be challenged and removed August 2020 Learn how and when to remove this template message The helium atom Depicted are the nucleus pink and the electron cloud distribution black The nucleus upper right in helium 4 is in reality spherically symmetric and closely resembles the electron cloud although for more complicated nuclei this is not always the case In quantum mechanics In the perspective of quantum mechanics helium is the second simplest atom to model following the hydrogen atom Helium is composed of two electrons in atomic orbitals surrounding a nucleus containing two protons and usually two neutrons As in Newtonian mechanics no system that consists of more than two particles can be solved with an exact analytical mathematical approach see 3 body problem and helium is no exception Thus numerical mathematical methods are required even to solve the system of one nucleus and two electrons Such computational chemistry methods have been used to create a quantum mechanical picture of helium electron binding which is accurate to within lt 2 of the correct value in a few computational steps 84 Such models show that each electron in helium partly screens the nucleus from the other so that the effective nuclear charge Zeff which each electron sees is about 1 69 units not the 2 charges of a classic bare helium nucleus Related stability of the helium 4 nucleus and electron shell The nucleus of the helium 4 atom is identical with an alpha particle High energy electron scattering experiments show its charge to decrease exponentially from a maximum at a central point exactly as does the charge density of helium s own electron cloud This symmetry reflects similar underlying physics the pair of neutrons and the pair of protons in helium s nucleus obey the same quantum mechanical rules as do helium s pair of electrons although the nuclear particles are subject to a different nuclear binding potential so that all these fermions fully occupy 1s orbitals in pairs none of them possessing orbital angular momentum and each cancelling the other s intrinsic spin Adding another of any of these particles would require angular momentum and would release substantially less energy in fact no nucleus with five nucleons is stable This arrangement is thus energetically extremely stable for all these particles and this stability accounts for many crucial facts regarding helium in nature For example the stability and low energy of the electron cloud state in helium accounts for the element s chemical inertness and also the lack of interaction of helium atoms with each other producing the lowest melting and boiling points of all the elements In a similar way the particular energetic stability of the helium 4 nucleus produced by similar effects accounts for the ease of helium 4 production in atomic reactions that involve either heavy particle emission or fusion Some stable helium 3 two protons and one neutron is produced in fusion reactions from hydrogen but it is a very small fraction compared to the highly favorable helium 4 Binding energy per nucleon of common isotopes The binding energy per particle of helium 4 is significantly larger than all nearby nuclides The unusual stability of the helium 4 nucleus is also important cosmologically it explains the fact that in the first few minutes after the Big Bang as the soup of free protons and neutrons which had initially been created in about 6 1 ratio cooled to the point that nuclear binding was possible almost all first compound atomic nuclei to form were helium 4 nuclei Owing to the relatively tight binding of helium 4 nuclei its production consumed nearly all of the free neutrons in a few minutes before they could beta decay and thus few neutrons were available to form heavier atoms such as lithium beryllium or boron Helium 4 nuclear binding per nucleon is stronger than in any of these elements see nucleogenesis and binding energy and thus once helium had been formed no energetic drive was available to make elements 3 4 and 5 85 It is barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon carbon However due to lack of intermediate elements this process requires three helium nuclei striking each other nearly simultaneously see triple alpha process There was thus no time for significant carbon to be formed in the few minutes after the Big Bang before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible This left the early universe with a very similar ratio of hydrogen helium as is observed today 3 parts hydrogen to 1 part helium 4 by mass with nearly all the neutrons in the universe trapped in helium 4 All heavier elements including those necessary for rocky planets like the Earth and for carbon based or other life have thus been created since the Big Bang in stars which were hot enough to fuse helium itself All elements other than hydrogen and helium today account for only 2 of the mass of atomic matter in the universe Helium 4 by contrast makes up about 23 of the universe s ordinary matter nearly all the ordinary matter that is not hydrogen Gas and plasma phases Helium discharge tube shaped into He the element s symbol Helium is the second least reactive noble gas after neon and thus the second least reactive of all elements 86 It is chemically inert and monatomic in all standard conditions Because of helium s relatively low molar atomic mass its thermal conductivity specific heat and sound speed in the gas phase are all greater than any other gas except hydrogen For these reasons and the small size of helium monatomic molecules helium diffuses through solids at a rate three times that of air and around 65 that of hydrogen 27 Helium is the least water soluble monatomic gas 87 and one of the least water soluble of any gas CF4 SF6 and C4F8 have lower mole fraction solubilities 0 3802 0 4394 and 0 2372 x2 10 5 respectively versus helium s 0 70797 x2 10 5 88 and helium s index of refraction is closer to unity than that of any other gas 89 Helium has a negative Joule Thomson coefficient at normal ambient temperatures meaning it heats up when allowed to freely expand Only below its Joule Thomson inversion temperature of about 32 to 50 K at 1 atmosphere does it cool upon free expansion 27 Once precooled below this temperature helium can be liquefied through expansion cooling Most extraterrestrial helium is plasma in stars with properties quite different from those of atomic helium In a plasma helium s electrons are not bound to its nucleus resulting in very high electrical conductivity even when the gas is only partially ionized The charged particles are highly influenced by magnetic and electric fields For example in the solar wind together with ionized hydrogen the particles interact with the Earth s magnetosphere giving rise to Birkeland currents and the aurora 90 Liquid phase Main article Liquid helium Liquefied helium This helium is not only liquid but has been cooled to the point of superfluidity The drop of liquid at the bottom of the glass represents helium spontaneously escaping from the container over the side to empty out of the container The energy to drive this process is supplied by the potential energy of the falling helium Unlike any other element helium will remain liquid down to absolute zero at normal pressures This is a direct effect of quantum mechanics specifically the zero point energy of the system is too high to allow freezing Solid helium requires a temperature of 1 1 5 K about 272 C or 457 F at about 25 bar 2 5 MPa of pressure 91 It is often hard to distinguish solid from liquid helium since the refractive index of the two phases are nearly the same The solid has a sharp melting point and has a crystalline structure but it is highly compressible applying pressure in a laboratory can decrease its volume by more than 30 92 With a bulk modulus of about 27 MPa 93 it is 100 times more compressible than water Solid helium has a density of 0 214 0 006 g cm3 at 1 15 K and 66 atm the projected density at 0 K and 25 bar 2 5 MPa is 0 187 0 009 g cm3 94 At higher temperatures helium will solidify with sufficient pressure At room temperature this requires about 114 000 atm 95 Helium I Below its boiling point of 4 22 K 268 93 C 452 07 F and above the lambda point of 2 1768 K 270 9732 C 455 7518 F the isotope helium 4 exists in a normal colorless liquid state called helium I 27 Like other cryogenic liquids helium I boils when it is heated and contracts when its temperature is lowered Below the lambda point however helium does not boil and it expands as the temperature is lowered further Helium I has a gas like index of refraction of 1 026 which makes its surface so hard to see that floats of Styrofoam are often used to show where the surface is 27 This colorless liquid has a very low viscosity and a density of 0 145 0 125 g mL between about 0 and 4 K 96 which is only one fourth the value expected from classical physics 27 Quantum mechanics is needed to explain this property and thus both states of liquid helium helium I and helium II are called quantum fluids meaning they display atomic properties on a macroscopic scale This may be an effect of its boiling point being so close to absolute zero preventing random molecular motion thermal energy from masking the atomic properties 27 Helium II Main article Superfluid helium 4 Liquid helium below its lambda point called helium II exhibits very unusual characteristics Due to its high thermal conductivity when it boils it does not bubble but rather evaporates directly from its surface Helium 3 also has a superfluid phase but only at much lower temperatures as a result less is known about the properties of the isotope 27 Unlike ordinary liquids helium II will creep along surfaces in order to reach an equal level after a short while the levels in the two containers will equalize The Rollin film also covers the interior of the larger container if it were not sealed the helium II would creep out and escape 27 Helium II is a superfluid a quantum mechanical state see macroscopic quantum phenomena of matter with strange properties For example when it flows through capillaries as thin as 10 7 to 10 8 m it has no measurable viscosity 25 However when measurements were done between two moving discs a viscosity comparable to that of gaseous helium was observed Current theory explains this using the two fluid model for helium II In this model liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a ground state which are superfluid and flow with exactly zero viscosity and a proportion of helium atoms in an excited state which behave more like an ordinary fluid 97 In the fountain effect a chamber is constructed which is connected to a reservoir of helium II by a sintered disc through which superfluid helium leaks easily but through which non superfluid helium cannot pass If the interior of the container is heated the superfluid helium changes to non superfluid helium In order to maintain the equilibrium fraction of superfluid helium superfluid helium leaks through and increases the pressure causing liquid to fountain out of the container 98 The thermal conductivity of helium II is greater than that of any other known substance a million times that of helium I and several hundred times that of copper 27 This is because heat conduction occurs by an exceptional quantum mechanism Most materials that conduct heat well have a valence band of free electrons which serve to transfer the heat Helium II has no such valence band but nevertheless conducts heat well The flow of heat is governed by equations that are similar to the wave equation used to characterize sound propagation in air When heat is introduced it moves at 20 meters per second at 1 8 K through helium II as waves in a phenomenon known as second sound 27 Helium II also exhibits a creeping effect When a surface extends past the level of helium II the helium II moves along the surface against the force of gravity Helium II will escape from a vessel that is not sealed by creeping along the sides until it reaches a warmer region where it evaporates It moves in a 30 nm thick film regardless of surface material This film is called a Rollin film and is named after the man who first characterized this trait Bernard V Rollin 27 99 100 As a result of this creeping behavior and helium II s ability to leak rapidly through tiny openings it is very difficult to confine Unless the container is carefully constructed the helium II will creep along the surfaces and through valves until it reaches somewhere warmer where it will evaporate Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water but rather than gravity the restoring force is the van der Waals force 101 These waves are known as third sound 102 Isotopes Main article Isotopes of helium There are nine known isotopes of helium of which two helium 3 and helium 4 are stable In the Earth s atmosphere one atom is 3 He for every million that are 4 He 25 Unlike most elements helium s isotopic abundance varies greatly by origin due to the different formation processes The most common isotope helium 4 is produced on Earth by alpha decay of heavier radioactive elements the alpha particles that emerge are fully ionized helium 4 nuclei Helium 4 is an unusually stable nucleus because its nucleons are arranged into complete shells It was also formed in enormous quantities during Big Bang nucleosynthesis 103 Helium 3 is present on Earth only in trace amounts Most of it has been present since Earth s formation though some falls to Earth trapped in cosmic dust 104 Trace amounts are also produced by the beta decay of tritium 105 Rocks from the Earth s crust have isotope ratios varying by as much as a factor of ten and these ratios can be used to investigate the origin of rocks and the composition of the Earth s mantle 104 3 He is much more abundant in stars as a product of nuclear fusion Thus in the interstellar medium the proportion of 3 He to 4 He is about 100 times higher than on Earth 106 Extraplanetary material such as lunar and asteroid regolith have trace amounts of helium 3 from being bombarded by solar winds The Moon s surface contains helium 3 at concentrations on the order of 10 ppb much higher than the approximately 5 ppt found in the Earth s atmosphere 107 108 A number of people starting with Gerald Kulcinski in 1986 109 have proposed to explore the moon mine lunar regolith and use the helium 3 for fusion Liquid helium 4 can be cooled to about 1 K 272 15 C 457 87 F using evaporative cooling in a 1 K pot Similar cooling of helium 3 which has a lower boiling point can achieve about 0 2 kelvin in a helium 3 refrigerator Equal mixtures of liquid 3 He and 4 He below 0 8 K separate into two immiscible phases due to their dissimilarity they follow different quantum statistics helium 4 atoms are bosons while helium 3 atoms are fermions 27 Dilution refrigerators use this immiscibility to achieve temperatures of a few millikelvins 110 It is possible to produce exotic helium isotopes which rapidly decay into other substances The shortest lived heavy helium isotope is the unbound helium 10 with a half life of 2 6 4 10 22 s 5 Helium 6 decays by emitting a beta particle and has a half life of 0 8 second Helium 7 and helium 8 are created in certain nuclear reactions 27 Helium 6 and helium 8 are known to exhibit a nuclear halo 27 Properties Table of thermal and physical properties of helium gas at atmospheric pressure 111 112 Temperature K Density kg m 3 Specific heat kJ kg C Dynamic viscosity kg m s Kinematic viscosity m 2 s Thermal conductivity W m C Thermal diffusivity m 2 s Prandtl Number100 5 193 9 63E 06 1 98E 05 0 073 2 89E 05 0 686120 0 406 5 193 1 07E 05 2 64E 05 0 0819 3 88E 05 0 679144 0 3379 5 193 1 26E 05 3 71E 05 0 0928 5 28E 05 0 7200 0 2435 5 193 1 57E 05 6 44E 05 0 1177 9 29E 05 0 69255 0 1906 5 193 1 82E 05 9 55E 05 0 1357 1 37E 04 0 7366 0 1328 5 193 2 31E 05 1 74E 04 0 1691 2 45E 04 0 71477 0 10204 5 193 2 75E 05 2 69E 04 0 197 3 72E 04 0 72589 0 08282 5 193 3 11E 05 3 76E 04 0 225 5 22E 04 0 72700 0 07032 5 193 3 48E 05 4 94E 04 0 251 6 66E 04 0 72800 0 06023 5 193 3 82E 05 6 34E 04 0 275 8 77E 04 0 72900 0 05451 5 193 4 14E 05 7 59E 04 0 33 1 14E 03 0 6871000 5 193 4 46E 05 9 14E 04 0 354 1 40E 03 0 654CompoundsMain article Helium compounds Structure of the helium hydride ion HHe Structure of the suspected fluoroheliate anion OHeF Helium has a valence of zero and is chemically unreactive under all normal conditions 92 It is an electrical insulator unless ionized As with the other noble gases helium has metastable energy levels that allow it to remain ionized in an electrical discharge with a voltage below its ionization potential 27 Helium can form unstable compounds known as excimers with tungsten iodine fluorine sulfur and phosphorus when it is subjected to a glow discharge to electron bombardment or reduced to plasma by other means The molecular compounds HeNe HgHe10 and WHe2 and the molecular ions He 2 He2 2 HeH and HeD have been created this way 113 HeH is also stable in its ground state but is extremely reactive it is the strongest Bronsted acid known and therefore can exist only in isolation as it will protonate any molecule or counteranion it contacts This technique has also produced the neutral molecule He2 which has a large number of band systems and HgHe which is apparently held together only by polarization forces 27 Van der Waals compounds of helium can also be formed with cryogenic helium gas and atoms of some other substance such as LiHe and He2 114 Theoretically other true compounds may be possible such as helium fluorohydride HHeF which would be analogous to HArF discovered in 2000 115 Calculations show that two new compounds containing a helium oxygen bond could be stable 116 Two new molecular species predicted using theory CsFHeO and N CH3 4FHeO are derivatives of a metastable FHeO anion first theorized in 2005 by a group from Taiwan If confirmed by experiment the only remaining element with no known stable compounds would be neon 117 Helium atoms have been inserted into the hollow carbon cage molecules the fullerenes by heating under high pressure The endohedral fullerene molecules formed are stable at high temperatures When chemical derivatives of these fullerenes are formed the helium stays inside 118 If helium 3 is used it can be readily observed by helium nuclear magnetic resonance spectroscopy 119 Many fullerenes containing helium 3 have been reported Although the helium atoms are not attached by covalent or ionic bonds these substances have distinct properties and a definite composition like all stoichiometric chemical compounds Under high pressures helium can form compounds with various other elements Helium nitrogen clathrate He N2 11 crystals have been grown at room temperature at pressures ca 10 GPa in a diamond anvil cell 120 The insulating electride Na2He has been shown to be thermodynamically stable at pressures above 113 GPa It has a fluorite structure 121 Occurrence and productionNatural abundance Although it is rare on Earth helium is the second most abundant element in the known Universe constituting 23 of its baryonic mass Only hydrogen is more abundant 25 The vast majority of helium was formed by Big Bang nucleosynthesis one to three minutes after the Big Bang As such measurements of its abundance contribute to cosmological models In stars it is formed by the nuclear fusion of hydrogen in proton proton chain reactions and the CNO cycle part of stellar nucleosynthesis 103 In the Earth s atmosphere the concentration of helium by volume is only 5 2 parts per million 122 123 The concentration is low and fairly constant despite the continuous production of new helium because most helium in the Earth s atmosphere escapes into space by several processes 124 125 126 In the Earth s heterosphere a part of the upper atmosphere helium and other lighter gases are the most abundant elements Most helium on Earth is a result of radioactive decay Helium is found in large amounts in minerals of uranium and thorium including uraninite and its varieties cleveite and pitchblende 17 127 carnotite and monazite a group name monazite usually refers to monazite Ce 128 129 because they emit alpha particles helium nuclei He2 to which electrons immediately combine as soon as the particle is stopped by the rock In this way an estimated 3000 metric tons of helium are generated per year throughout the lithosphere 130 131 132 In the Earth s crust the concentration of helium is 8 parts per billion In seawater the concentration is only 4 parts per trillion There are also small amounts in mineral springs volcanic gas and meteoric iron Because helium is trapped in the subsurface under conditions that also trap natural gas the greatest natural concentrations of helium on the planet are found in natural gas from which most commercial helium is extracted The concentration varies in a broad range from a few ppm to more than 7 in a small gas field in San Juan County New Mexico 133 134 As of 2021 update the world s helium reserves were estimated at 31 billion cubic meters with a third of that being in Qatar 135 In 2015 and 2016 additional probable reserves were announced to be under the Rocky Mountains in North America 136 and in the East African Rift 137 Modern extraction and distribution For large scale use helium is extracted by fractional distillation from natural gas which can contain as much as 7 helium 138 Since helium has a lower boiling point than any other element low temperature and high pressure are used to liquefy nearly all the other gases mostly nitrogen and methane The resulting crude helium gas is purified by successive exposures to lowering temperatures in which almost all of the remaining nitrogen and other gases are precipitated out of the gaseous mixture Activated charcoal is used as a final purification step usually resulting in 99 995 pure Grade A helium 27 The principal impurity in Grade A helium is neon In a final production step most of the helium that is produced is liquefied via a cryogenic process This is necessary for applications requiring liquid helium and also allows helium suppliers to reduce the cost of long distance transportation as the largest liquid helium containers have more than five times the capacity of the largest gaseous helium tube trailers 76 139 In 2008 approximately 169 million standard cubic meters SCM of helium were extracted from natural gas or withdrawn from helium reserves with approximately 78 from the United States 10 from Algeria and most of the remainder from Russia Poland and Qatar 140 By 2013 increases in helium production in Qatar under the company Qatargas managed by Air Liquide had increased Qatar s fraction of world helium production to 25 and made it the second largest exporter after the United States 141 An estimated 54 billion cubic feet 1 5 109 m3 deposit of helium was found in Tanzania in 2016 142 A large scale helium plant was opened in Ningxia China in 2020 143 In the United States most helium is extracted from natural gas of the Hugoton and nearby gas fields in Kansas Oklahoma and the Panhandle Field in Texas 76 144 Much of this gas was once sent by pipeline to the National Helium Reserve but since 2005 this reserve is being depleted and sold off and is expected to be largely depleted by 2021 141 under the October 2013 Responsible Helium Administration and Stewardship Act H R 527 145 Diffusion of crude natural gas through special semipermeable membranes and other barriers is another method to recover and purify helium 146 In 1996 the U S had proven helium reserves in such gas well complexes of about 147 billion standard cubic feet 4 2 billion SCM 147 At rates of use at that time 72 million SCM per year in the U S see pie chart below this would have been enough helium for about 58 years of U S use and less than this perhaps 80 of the time at world use rates although factors in saving and processing impact effective reserve numbers Helium must be extracted from natural gas because it is present in air at only a fraction of that of neon yet the demand for it is far higher It is estimated that if all neon production were retooled to save helium 0 1 of the world s helium demands would be satisfied Similarly only 1 of the world s helium demands could be satisfied by re tooling all air distillation plants 148 Helium can be synthesized by bombardment of lithium or boron with high velocity protons or by bombardment of lithium with deuterons but these processes are a completely uneconomical method of production 149 Helium is commercially available in either liquid or gaseous form As a liquid it can be supplied in small insulated containers called dewars which hold as much as 1 000 liters of helium or in large ISO containers which have nominal capacities as large as 42 m3 around 11 000 U S gallons In gaseous form small quantities of helium are supplied in high pressure cylinders holding as much as 8 m3 approx 282 standard cubic feet while large quantities of high pressure gas are supplied in tube trailers which have capacities of as much as 4 860 m3 approx 172 000 standard cubic feet Conservation advocates Main article Helium storage and conservation According to helium conservationists like Nobel laureate physicist Robert Coleman Richardson writing in 2010 the free market price of helium has contributed to wasteful usage e g for helium balloons Prices in the 2000s had been lowered by the decision of the U S Congress to sell off the country s large helium stockpile by 2015 150 According to Richardson the price needed to be multiplied by 20 to eliminate the excessive wasting of helium In the paper Stop squandering helium published in 2012 it was also proposed to create an International Helium Agency that would build a sustainable market for this precious commodity 151 Applications The largest single use of liquid helium is to cool the superconducting magnets in modern MRI scanners Estimated 2014 U S fractional helium use by category Total use is 34 million cubic meters 152 Cryogenics 32 Pressurizing and purging 18 Welding 13 Controlled atmospheres 18 Leak detection 4 Breathing mixtures 2 Other 13 While balloons are perhaps the best known use of helium they are a minor part of all helium use 71 Helium is used for many purposes that require some of its unique properties such as its low boiling point low density low solubility high thermal conductivity or inertness Of the 2014 world helium total production of about 32 million kg 180 million standard cubic meters helium per year the largest use about 32 of the total in 2014 is in cryogenic applications most of which involves cooling the superconducting magnets in medical MRI scanners and NMR spectrometers 153 Other major uses were pressurizing and purging systems welding maintenance of controlled atmospheres and leak detection Other uses by category were relatively minor fractions 152 Controlled atmospheres Helium is used as a protective gas in growing silicon and germanium crystals in titanium and zirconium production and in gas chromatography 92 because it is inert Because of its inertness thermally and calorically perfect nature high speed of sound and high value of the heat capacity ratio it is also useful in supersonic wind tunnels 154 and impulse facilities 155 Gas tungsten arc welding Main article Gas tungsten arc welding Helium is used as a shielding gas in arc welding processes on materials that at welding temperatures are contaminated and weakened by air or nitrogen 25 A number of inert shielding gases are used in gas tungsten arc welding but helium is used instead of cheaper argon especially for welding materials that have higher heat conductivity like aluminium or copper Minor uses Industrial leak detection A dual chamber helium leak detection machine One industrial application for helium is leak detection Because helium diffuses through solids three times faster than air it is used as a tracer gas to detect leaks in high vacuum equipment such as cryogenic tanks and high pressure containers 156 The tested object is placed in a chamber which is then evacuated and filled with helium The helium that escapes through the leaks is detected by a sensitive device helium mass spectrometer even at the leak rates as small as 10 9 mbar L s 10 10 Pa m3 s The measurement procedure is normally automatic and is called helium integral test A simpler procedure is to fill the tested object with helium and to manually search for leaks with a hand held device 157 Helium leaks through cracks should not be confused with gas permeation through a bulk material While helium has documented permeation constants thus a calculable permeation rate through glasses ceramics and synthetic materials inert gases such as helium will not permeate most bulk metals 158 Flight Because of its low density and incombustibility helium is the gas of choice to fill airships such as the Goodyear blimp Because it is lighter than air airships and balloons are inflated with helium for lift While hydrogen gas is more buoyant and escapes permeating through a membrane at a lower rate helium has the advantage of being non flammable and indeed fire retardant Another minor use is in rocketry where helium is used as an ullage medium to backfill rocket propellant tanks in flight and to condense hydrogen and oxygen to make rocket fuel It is also used to purge fuel and oxidizer from ground support equipment prior to launch and to pre cool liquid hydrogen in space vehicles For example the Saturn V rocket used in the Apollo program needed about 370 000 m3 13 million cubic feet of helium to launch 92 Minor commercial and recreational uses Helium as a breathing gas has no narcotic properties so helium mixtures such as trimix heliox and heliair are used for deep diving to reduce the effects of narcosis which worsen with increasing depth 159 160 As pressure increases with depth the density of the breathing gas also increases and the low molecular weight of helium is found to considerably reduce the effort of breathing by lowering the density of the mixture This reduces the Reynolds number of flow leading to a reduction of turbulent flow and an increase in laminar flow which requires less work of breathing 161 162 At depths below 150 metres 490 ft divers breathing helium oxygen mixtures begin to experience tremors and a decrease in psychomotor function symptoms of high pressure nervous syndrome 163 This effect may be countered to some extent by adding an amount of narcotic gas such as hydrogen or nitrogen to a helium oxygen mixture 164 Helium neon lasers a type of low powered gas laser producing a red beam had various practical applications which included barcode readers and laser pointers before they were almost universally replaced by cheaper diode lasers 25 For its inertness and high thermal conductivity neutron transparency and because it does not form radioactive isotopes under reactor conditions helium is used as a heat transfer medium in some gas cooled nuclear reactors 156 Helium mixed with a heavier gas such as xenon is useful for thermoacoustic refrigeration due to the resulting high heat capacity ratio and low Prandtl number 165 The inertness of helium has environmental advantages over conventional refrigeration systems which contribute to ozone depletion or global warming 166 Helium is also used in some hard disk drives 167 Scientific uses The use of helium reduces the distorting effects of temperature variations in the space between lenses in some telescopes due to its extremely low index of refraction 27 This method is especially used in solar telescopes where a vacuum tight telescope tube would be too heavy 168 169 Helium is a commonly used carrier gas for gas chromatography The age of rocks and minerals that contain uranium and thorium can be estimated by measuring the level of helium with a process known as helium dating 25 27 Helium at low temperatures is used in cryogenics and in certain cryogenics applications As examples of applications liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity such as in superconducting magnets for magnetic resonance imaging The Large Hadron Collider at CERN uses 96 metric tons of liquid helium to maintain the temperature at 1 9 K 271 25 C 456 25 F 170 Medical uses Helium was approved for medical use in the United States in April 2020 for humans and animals 171 172 As a contaminantWhile chemically inert helium contamination impairs the operation of microelectromechanical systems MEMS such that iPhones may fail 173 Inhalation and safetyEffects Neutral helium at standard conditions is non toxic plays no biological role and is found in trace amounts in human blood Effect of helium on a human voice source source The effect of helium on a human voice Problems playing this file See media help The speed of sound in helium is nearly three times the speed of sound in air Because the natural resonance frequency of a gas filled cavity is proportional to the speed of sound in the gas when helium is inhaled a corresponding increase occurs in the resonant frequencies of the vocal tract which is the amplifier of vocal sound 25 174 This increase in the resonant frequency of the amplifier the vocal tract gives an increased amplification to the high frequency components of the sound wave produced by the direct vibration of the vocal folds compared to the case when the voice box is filled with air When a person speaks after inhaling helium gas the muscles that control the voice box still move in the same way as when the voice box is filled with air therefore the fundamental frequency sometimes called pitch produced by direct vibration of the vocal folds does not change 175 However the high frequency preferred amplification causes a change in timbre of the amplified sound resulting in a reedy duck like vocal quality The opposite effect lowering resonant frequencies can be obtained by inhaling a dense gas such as sulfur hexafluoride or xenon Hazards Inhaling helium can be dangerous if done to excess since helium is a simple asphyxiant and so displaces oxygen needed for normal respiration 25 176 Fatalities have been recorded including a youth who suffocated in Vancouver in 2003 and two adults who suffocated in South Florida in 2006 177 178 In 1998 an Australian girl from Victoria fell unconscious and temporarily turned blue after inhaling the entire contents of a party balloon 179 180 181 Inhaling helium directly from pressurized cylinders or even balloon filling valves is extremely dangerous as high flow rate and pressure can result in barotrauma fatally rupturing lung tissue 176 182 Death caused by helium is rare The first media recorded case was that of a 15 year old girl from Texas who died in 1998 from helium inhalation at a friend s party the exact type of helium death is unidentified 179 180 181 In the United States only two fatalities were reported between 2000 and 2004 including a man who died in North Carolina of barotrauma in 2002 177 182 A youth asphyxiated in Vancouver during 2003 and a 27 year old man in Australia had an embolism after breathing from a cylinder in 2000 177 Since then two adults asphyxiated in South Florida in 2006 177 178 183 and there were cases in 2009 and 2010 one a Californian youth who was found with a bag over his head attached to a helium tank 184 and another teenager in Northern Ireland died of asphyxiation 185 At Eagle Point Oregon a teenage girl died in 2012 from barotrauma at a party 186 187 188 A girl from Michigan died from hypoxia later in the year 189 On February 4 2015 it was revealed that during the recording of their main TV show on January 28 a 12 year old member name withheld of Japanese all girl singing group 3B Junior suffered from air embolism losing consciousness and falling into a coma as a result of air bubbles blocking the flow of blood to the brain after inhaling huge quantities of helium as part of a game The incident was not made public until a week later 190 191 The staff of TV Asahi held an emergency press conference to communicate that the member had been taken to the hospital and is showing signs of rehabilitation such as moving eyes and limbs but her consciousness has not yet been sufficiently recovered Police have launched an investigation due to a neglect of safety measures 192 193 The safety issues for cryogenic helium are similar to those of liquid nitrogen its extremely low temperatures can result in cold burns and the liquid to gas expansion ratio can cause explosions if no pressure relief devices are installed Containers of helium gas at 5 to 10 K should be handled as if they contain liquid helium due to the rapid and significant thermal expansion that occurs when helium gas at less than 10 K is warmed to room temperature 92 At high pressures more than about 20 atm or two MPa a mixture of helium and oxygen heliox can lead to high pressure nervous syndrome a sort of reverse anesthetic effect adding a small amount of nitrogen to the mixture can alleviate the problem 194 163 See alsoAbiogenic petroleum origin Helium 3 propulsion Leidenfrost effect Superfluid Tracer gas leak testing method Hamilton Cady Portal ChemistryHelium at Wikipedia s sister projects Definitions from Wiktionary Media from Commons Textbooks from Wikibooks Resources from WikiversityNotes A few authors dispute the placement of helium in the noble gas column preferring to place it above beryllium with the alkaline earth metals They do so on the grounds of helium s 1s2 electron configuration which is analogous to the ns2 valence configurations of the alkaline earth metals and furthermore point to some specific trends that are more regular with helium over beryllium 6 7 8 9 10 However the classification of helium with the other noble gases remains near universal as its extraordinary inertness is extremely close to that of the other light noble gases neon and argon 11 References Standard Atomic Weights Helium CIAAW 1983 Shuen Chen Hwang Robert D Lein Daniel A Morgan 2005 Noble Gases Kirk Othmer Encyclopedia of Chemical Technology Wiley pp 343 383 doi 10 1002 0471238961 0701190508230114 a01 Magnetic susceptibility of the elements and inorganic compounds in Handbook of Chemistry and Physics 81st edition CRC press Weast Robert 1984 CRC Handbook of Chemistry and Physics Boca Raton Florida Chemical Rubber Company Publishing pp E110 ISBN 0 8493 0464 4 a b Kondev F G Wang M Huang W J Naimi S Audi G 2021 The NUBASE2020 evaluation of nuclear properties PDF Chinese Physics C 45 3 030001 doi 10 1088 1674 1137 abddae Grochala Wojciech 1 November 2017 On the position of helium and neon in the Periodic Table of Elements Foundations of Chemistry 20 2018 191 207 doi 10 1007 s10698 017 9302 7 Bent Weberg Libby 18 January 2019 The periodic table Chemical amp Engineering News 97 3 Retrieved 27 March 2020 Grandinetti Felice 23 April 2013 Neon behind the signs Nature Chemistry 5 2013 438 Bibcode 2013NatCh 5 438G doi 10 1038 nchem 1631 PMID 23609097 Kurushkin Mikhail 2020 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devoir etre assimilees aux lignes principales du spectre solaire B D E b une ligne inconnue F et deux lignes du groupe G I saw immediately a series of nine bright lines that seemed to me should be classed as the principal lines of the solar spectrum B D E b an unknown line F and two lines of the group G Captain C T Haig 1868 Account of spectroscopic observations of the eclipse of the sun August 18th 1868 Proceedings of the Royal Society of London 17 74 80 From p 74 I may state at once that I observed the spectra of two red flames close to each other and in their spectra two broad bright bands quite sharply defined one rose madder and the other light golden Pogson filed his observations of the 1868 eclipse with the local Indian government but his report wasn t published Biman B Nath The Story of Helium and the Birth of Astrophysics New York New York Springer 2013 p 8 Nevertheless Lockyer quoted from his report From p 320 Archived 17 August 2018 at the Wayback Machine of Lockyer J Norman 1896 The story of helium Prologue Nature 53 319 322 Pogson in referring to the eclipse of 1868 said that the yellow line was at D or near D Lieutenant John Herschel 1868 Account of the solar eclipse of 1868 as seen at Jamkandi in the Bombay Presidency Proceedings of the Royal Society of London 17 104 120 From p 113 As the moment of the total solar eclipse approached I recorded an increasing brilliancy in the spectrum in the neighborhood of D so great in fact as to prevent any measurement of that line till an opportune cloud moderated the light I am not prepared to offer any explanation of this From p 117 I also consider that there can be no question that the ORANGE LINE was identical with D so far as the capacity of the instrument to establish any such identity is concerned In his initial report to the French Academy of Sciences about the 1868 eclipse Janssen made no mention of a yellow line in the solar spectrum See Janssen 1868 Indication de quelques uns des resultats obtenus a Cocanada pendant l eclipse du mois d aout dernier et a la suite de cette eclipse Information on some of the results obtained at Cocanada during the eclipse of the month of last August and following that eclipse Comptes rendus 67 838 839 Wheeler M Sears Helium The Disappearing Element Heidelberg Germany Springer 2015 p 44 Francoise Launay with Storm Dunlop trans The Astronomer Jules Janssen A Globetrotter of Celestial Physics Heidelberg Germany Springer 2012 p 45 However subsequently in an unpublished letter of 19 December 1868 to Charles Sainte Claire Deville Janssen asked Deville to inform the French Academy of Sciences that Several observers have claimed the bright D line as forming part of the spectrum of the prominences on 18 August The bright yellow line did indeed lie very close to D but the light was more refrangible i e of shorter wavelength than those of the D lines My subsequent studies of the Sun have shown the accuracy of what I state here See Launay 2012 p 45 a b Cleveite 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General U S Government s Bureau of Land Management Sources Refinement and Shortage With some history of helium U S Geological Survey publications on helium beginning 1996 Helium Where is all the helium Aga website It s Elemental Helium Chemistry in its element podcast MP3 from the Royal Society of Chemistry s Chemistry World Helium International Chemical Safety Cards Helium includes health and safety information regarding accidental exposures to heliumMore detail Helium at The Periodic Table of Videos University of Nottingham Helium at the Helsinki University of Technology includes pressure temperature phase diagrams for helium 3 and helium 4 Lancaster University Ultra Low Temperature Physics includes a summary of some low temperature techniques Video Demonstration of superfluid helium Alfred Leitner 1963 38 min Miscellaneous Physics in Speech with audio samples that demonstrate the unchanged voice pitch Article about helium and other noble gasesHelium shortage America s Helium Supply Options for Producing More Helium from Federal Land Oversight Hearing before the Subcommittee on Energy and Mineral Resources of the Committee on Natural Resources U S House Of Representatives One Hundred Thirteenth Congress First Session Thursday July 11 2013 Helium Program Urgent Issues Facing BLM s Storage and Sale of Helium Reserves Testimony before the Committee on Natural Resources House of Representatives Government Accountability Office Kramer David May 22 2012 Senate bill would preserve US helium reserve Measure would give scientists first dibs on helium should a shortage develop Physics Today web site Archived from the original on October 27 2012 Richardson Robert C Chan Moses 2009 Helium when will it run out PDF Archived from the original PDF on 2015 06 14 Retrieved from https en wikipedia org w index php title Helium amp oldid 1147992105, wikipedia, wiki, book, books, library,

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