Argon

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

Not to be confused with Aragon.

Argon is a chemical element; it has symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas.^[8] Argon is the third most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abundant as water vapor (which averages about 4000 ppmv, but varies greatly), 23 times as abundant as carbon dioxide (400 ppmv), and more than 500 times as abundant as neon (18 ppmv). Argon is the most abundant noble gas in Earth's crust, comprising 0.00015% of the crust.

Argon, ₁₈Ar

Argon
Pronunciation	/ˈɑːrɡɒn/ ​(AR-gon)
Appearance	colorless gas exhibiting a lilac/violet glow when placed in an electric field
Standard atomic weight Ar°(Ar)
	[39.792, 39.963]^[1] 39.95±0.16 (abridged)^[2]
Argon 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 Ne ↑ Ar ↓ Kr chlorine ← argon → potassium
Atomic number (Z)	18
Group	group 18 (noble gases)
Period	period 3
Block	p-block
Electron configuration	[Ne] 3s^2 3p^6
Electrons per shell	2, 8, 8
Physical properties
Phase at STP	gas
Melting point	83.81 K ​(−189.34 °C, ​−308.81 °F)
Boiling point	87.302 K ​(−185.848 °C, ​−302.526 °F)
Density (at STP)	1.784 g/L
when liquid (at b.p.)	1.3954 g/cm^3
Triple point	83.8058 K, ​68.89 kPa^[3]
Critical point	150.687 K, 4.863 MPa^[3]
Heat of fusion	1.18 kJ/mol
Heat of vaporization	6.53 kJ/mol
Molar heat capacity	20.85^[4] J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K)   47 53 61 71 87
Atomic properties
Oxidation states	0
Electronegativity	Pauling scale: no data
Ionization energies	1st: 1520.6 kJ/mol 2nd: 2665.8 kJ/mol 3rd: 3931 kJ/mol (more)
Covalent radius	106±10 pm
Van der Waals radius	188 pm
Spectral lines of argon
Other properties
Natural occurrence	primordial
Crystal structure	​face-centered cubic (fcc)
Thermal conductivity	17.72×10^−3  W/(m⋅K)
Magnetic ordering	diamagnetic^[5]
Molar magnetic susceptibility	−19.6×10^−6 cm^3/mol^[6]
Speed of sound	323 m/s (gas, at 27 °C)
CAS Number	7440-37-1
History
Discovery and first isolation	Lord Rayleigh and William Ramsay (1894)
Isotopes of argon v e
Main isotopes^[7] Decay abun­dance half-life (t1/2) mode pro­duct ^36Ar 0.334% stable ^37Ar trace 35 d ε ^37Cl ^38Ar 0.0630% stable ^39Ar trace 268 y β^− ^39K ^40Ar 99.6% stable ^41Ar trace 109.34 min β^− ^41K ^42Ar synth 32.9 y β^− ^42K
Category: Argon view talk edit | references

Nearly all argon in Earth's atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in Earth's crust. In the universe, argon-36 is by far the most common argon isotope, as it is the most easily produced by stellar nucleosynthesis in supernovas.

The name "argon" is derived from the Greek word ἀργόν, neuter singular form of ἀργός meaning 'lazy' or 'inactive', as a reference to the fact that the element undergoes almost no chemical reactions. The complete octet (eight electrons) in the outer atomic shell makes argon stable and resistant to bonding with other elements. Its triple point temperature of 83.8058 K is a defining fixed point in the International Temperature Scale of 1990.

Argon is extracted industrially by the fractional distillation of liquid air. It is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning. It is also used in incandescent, fluorescent lighting, and other gas-discharge tubes. It makes a distinctive blue-green gas laser. It is also used in fluorescent glow starters.

Characteristics

 

A small piece of rapidly melting solid argon

Argon has approximately the same solubility in water as oxygen and is 2.5 times more soluble in water than nitrogen. Argon is colorless, odorless, nonflammable and nontoxic as a solid, liquid or gas.^[9] Argon is chemically inert under most conditions and forms no confirmed stable compounds at room temperature.

Although argon is a noble gas, it can form some compounds under various extreme conditions. Argon fluorohydride (HArF), a compound of argon with fluorine and hydrogen that is stable below 17 K (−256.1 °C; −429.1 °F), has been demonstrated.^[10][11] Although the neutral ground-state chemical compounds of argon are presently limited to HArF, argon can form clathrates with water when atoms of argon are trapped in a lattice of water molecules.^[12] Ions, such as ArH⁺
, and excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more argon compounds that should be stable^[13] but have not yet been synthesized.

History

 

A: test-tube, B: dilute alkali, C: U-shaped glass tube, D: platinum electrode

Argon (Greek ἀργόν, neuter singular form of ἀργός meaning "lazy" or "inactive") is named in reference to its chemical inactivity. This chemical property of this first noble gas to be discovered impressed the namers.^[14][15] An unreactive gas was suspected to be a component of air by Henry Cavendish in 1785.^[16]

Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water, and nitrogen from a sample of clean air.^[17][18][19] They first accomplished this by replicating an experiment of Henry Cavendish's. They trapped a mixture of atmospheric air with additional oxygen in a test-tube (A) upside-down over a large quantity of dilute alkali solution (B), which in Cavendish's original experiment was potassium hydroxide,^[16] and conveyed a current through wires insulated by U-shaped glass tubes (CC) which sealed around the platinum wire electrodes, leaving the ends of the wires (DD) exposed to the gas and insulated from the alkali solution. The arc was powered by a battery of five Grove cells and a Ruhmkorff coil of medium size. The alkali absorbed the oxides of nitrogen produced by the arc and also carbon dioxide. They operated the arc until no more reduction of volume of the gas could be seen for at least an hour or two and the spectral lines of nitrogen disappeared when the gas was examined. The remaining oxygen was reacted with alkaline pyrogallate to leave behind an apparently non-reactive gas which they called argon.

 

Captioned "Argon", caricature of Lord Rayleigh in Vanity Fair, 1899

Before isolating the gas, they had determined that nitrogen produced from chemical compounds was 0.5% lighter than nitrogen from the atmosphere. The difference was slight, but it was important enough to attract their attention for many months. They concluded that there was another gas in the air mixed in with the nitrogen.^[20] Argon was also encountered in 1882 through independent research of H. F. Newall and W. N. Hartley.^[21] Each observed new lines in the emission spectrum of air that did not match known elements.

Until 1957, the symbol for argon was "A", but now it is "Ar".^[22]

Occurrence

Argon constitutes 0.934% by volume and 1.288% by mass of Earth's atmosphere.^[23] Air is the primary industrial source of purified argon products. Argon is isolated from air by fractionation, most commonly by cryogenic fractional distillation, a process that also produces purified nitrogen, oxygen, neon, krypton and xenon.^[24] Earth's crust and seawater contain 1.2 ppm and 0.45 ppm of argon, respectively.^[25]

Isotopes

Main article: Isotopes of argon

The main isotopes of argon found on Earth are ⁴⁰
Ar (99.6%), ³⁶
Ar (0.34%), and ³⁸
Ar (0.06%). Naturally occurring ⁴⁰
K, with a half-life of 1.25×10⁹ years, decays to stable ⁴⁰
Ar (11.2%) by electron capture or positron emission, and also to stable ⁴⁰
Ca (88.8%) by beta decay. These properties and ratios are used to determine the age of rocks by K–Ar dating.^[25][26]

In Earth's atmosphere, ³⁹
Ar is made by cosmic ray activity, primarily by neutron capture of ⁴⁰
Ar followed by two-neutron emission. In the subsurface environment, it is also produced through neutron capture by ³⁹
K, followed by proton emission. ³⁷
Ar is created from the neutron capture by ⁴⁰
Ca followed by an alpha particle emission as a result of subsurface nuclear explosions. It has a half-life of 35 days.^[26]

Between locations in the Solar System, the isotopic composition of argon varies greatly. Where the major source of argon is the decay of ⁴⁰
K in rocks, ⁴⁰
Ar will be the dominant isotope, as it is on Earth. Argon produced directly by stellar nucleosynthesis is dominated by the alpha-process nuclide ³⁶
Ar. Correspondingly, solar argon contains 84.6% ³⁶
Ar (according to solar wind measurements),^[27] and the ratio of the three isotopes ³⁶Ar : ³⁸Ar : ⁴⁰Ar in the atmospheres of the outer planets is 8400 : 1600 : 1.^[28] This contrasts with the low abundance of primordial ³⁶
Ar in Earth's atmosphere, which is only 31.5 ppmv (= 9340 ppmv × 0.337%), comparable with that of neon (18.18 ppmv) on Earth and with interplanetary gasses, measured by probes.

The atmospheres of Mars, Mercury and Titan (the largest moon of Saturn) contain argon, predominantly as ⁴⁰
Ar, and its content may be as high as 1.93% (Mars).^[29]

The predominance of radiogenic ⁴⁰
Ar is the reason the standard atomic weight of terrestrial argon is greater than that of the next element, potassium, a fact that was puzzling when argon was discovered. Mendeleev positioned the elements on his periodic table in order of atomic weight, but the inertness of argon suggested a placement before the reactive alkali metal. Henry Moseley later solved this problem by showing that the periodic table is actually arranged in order of atomic number (see History of the periodic table).

Compounds

Main article: Argon compounds

 

Space-filling model of argon fluorohydride

Argon's complete octet of electrons indicates full s and p subshells. This full valence shell makes argon very stable and extremely resistant to bonding with other elements. Before 1962, argon and the other noble gases were considered to be chemically inert and unable to form compounds; however, compounds of the heavier noble gases have since been synthesized. The first argon compound with tungsten pentacarbonyl, W(CO)₅Ar, was isolated in 1975. However, it was not widely recognised at that time.^[30] In August 2000, another argon compound, argon fluorohydride (HArF), was formed by researchers at the University of Helsinki, by shining ultraviolet light onto frozen argon containing a small amount of hydrogen fluoride with caesium iodide. This discovery caused the recognition that argon could form weakly bound compounds, even though it was not the first.^[11][31][32] It is stable up to 17 kelvins (−256 °C). The metastable ArCF²⁺
₂ dication, which is valence-isoelectronic with carbonyl fluoride and phosgene, was observed in 2010.^[33] Argon-36, in the form of argon hydride (argonium) ions, has been detected in interstellar medium associated with the Crab Nebula supernova; this was the first noble-gas molecule detected in outer space.^[34][35]

Solid argon hydride (Ar(H₂)₂) has the same crystal structure as the MgZn₂ Laves phase. It forms at pressures between 4.3 and 220 GPa, though Raman measurements suggest that the H₂ molecules in Ar(H₂)₂ dissociate above 175 GPa.^[36]

Production

Argon is extracted industrially by the fractional distillation of liquid air in a cryogenic air separation unit; a process that separates liquid nitrogen, which boils at 77.3 K, from argon, which boils at 87.3 K, and liquid oxygen, which boils at 90.2 K. About 700,000 tonnes of argon are produced worldwide every year.^[25][37]

Applications

 

Cylinders containing argon gas for use in extinguishing fire without damaging server equipment

Argon has several desirable properties:

• Argon is a chemically inert gas.
• Argon is the cheapest alternative when nitrogen is not sufficiently inert.
• Argon has low thermal conductivity.
• Argon has electronic properties (ionization and/or the emission spectrum) desirable for some applications.

Other noble gases would be equally suitable for most of these applications, but argon is by far the cheapest. It is inexpensive, since it occurs naturally in air and is readily obtained as a byproduct of cryogenic air separation in the production of liquid oxygen and liquid nitrogen: the primary constituents of air are used on a large industrial scale. The other noble gases (except helium) are produced this way as well, but argon is the most plentiful by far. The bulk of its applications arise simply because it is inert and relatively cheap.

Industrial processes

Argon is used in some high-temperature industrial processes where ordinarily non-reactive substances become reactive. For example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning.

For some of these processes, the presence of nitrogen or oxygen gases might cause defects within the material. Argon is used in some types of arc welding such as gas metal arc welding and gas tungsten arc welding, as well as in the processing of titanium and other reactive elements. An argon atmosphere is also used for growing crystals of silicon and germanium.

See also: shielding gas

Argon is used in the poultry industry to asphyxiate birds, either for mass culling following disease outbreaks, or as a means of slaughter more humane than electric stunning. Argon is denser than air and displaces oxygen close to the ground during inert gas asphyxiation.^[38][39] Its non-reactive nature makes it suitable in a food product, and since it replaces oxygen within the dead bird, argon also enhances shelf life.^[40]

Argon is sometimes used for extinguishing fires where valuable equipment may be damaged by water or foam.^[41]

Scientific research

Liquid argon is used as the target for neutrino experiments and direct dark matter searches. The interaction between the hypothetical WIMPs and an argon nucleus produces scintillation light that is detected by photomultiplier tubes. Two-phase detectors containing argon gas are used to detect the ionized electrons produced during the WIMP–nucleus scattering. As with most other liquefied noble gases, argon has a high scintillation light yield (about 51 photons/keV^[42]), is transparent to its own scintillation light, and is relatively easy to purify. Compared to xenon, argon is cheaper and has a distinct scintillation time profile, which allows the separation of electronic recoils from nuclear recoils. On the other hand, its intrinsic beta-ray background is larger due to ³⁹
Ar contamination, unless one uses argon from underground sources, which has much less ³⁹
Ar contamination. Most of the argon in Earth's atmosphere was produced by electron capture of long-lived ⁴⁰
K (⁴⁰
K + e⁻ → ⁴⁰
Ar + ν) present in natural potassium within Earth. The ³⁹
Ar activity in the atmosphere is maintained by cosmogenic production through the knockout reaction ⁴⁰
Ar(n,2n)³⁹
Ar and similar reactions. The half-life of ³⁹
Ar is only 269 years. As a result, the underground Ar, shielded by rock and water, has much less ³⁹
Ar contamination.^[43] Dark-matter detectors currently operating with liquid argon include DarkSide, WArP, ArDM, microCLEAN and DEAP. Neutrino experiments include ICARUS and MicroBooNE, both of which use high-purity liquid argon in a time projection chamber for fine grained three-dimensional imaging of neutrino interactions.

At Linköping University, Sweden, the inert gas is being utilized in a vacuum chamber in which plasma is introduced to ionize metallic films.^[44] This process results in a film usable for manufacturing computer processors. The new process would eliminate the need for chemical baths and use of expensive, dangerous and rare materials.

Preservative

 

A sample of caesium is packed under argon to avoid reactions with air

Argon is used to displace oxygen- and moisture-containing air in packaging material to extend the shelf-lives of the contents (argon has the European food additive code E938). Aerial oxidation, hydrolysis, and other chemical reactions that degrade the products are retarded or prevented entirely. High-purity chemicals and pharmaceuticals are sometimes packed and sealed in argon.^[45]

In winemaking, argon is used in a variety of activities to provide a barrier against oxygen at the liquid surface, which can spoil wine by fueling both microbial metabolism (as with acetic acid bacteria) and standard redox chemistry.

Argon is sometimes used as the propellant in aerosol cans.

Argon is also used as a preservative for such products as varnish, polyurethane, and paint, by displacing air to prepare a container for storage.^[46]

Since 2002, the American National Archives stores important national documents such as the Declaration of Independence and the Constitution within argon-filled cases to inhibit their degradation. Argon is preferable to the helium that had been used in the preceding five decades, because helium gas escapes through the intermolecular pores in most containers and must be regularly replaced.^[47]

Laboratory equipment

See also: Air-free technique

 

Gloveboxes are often filled with argon, which recirculates over scrubbers to maintain an oxygen-, nitrogen-, and moisture-free atmosphere

Argon may be used as the inert gas within Schlenk lines and gloveboxes. Argon is preferred to less expensive nitrogen in cases where nitrogen may react with the reagents or apparatus.

Argon may be used as the carrier gas in gas chromatography and in electrospray ionization mass spectrometry; it is the gas of choice for the plasma used in ICP spectroscopy. Argon is preferred for the sputter coating of specimens for scanning electron microscopy. Argon gas is also commonly used for sputter deposition of thin films as in microelectronics and for wafer cleaning in microfabrication.

Medical use

Cryosurgery procedures such as cryoablation use liquid argon to destroy tissue such as cancer cells. It is used in a procedure called "argon-enhanced coagulation", a form of argon plasma beam electrosurgery. The procedure carries a risk of producing gas embolism and has resulted in the death of at least one patient.^[48]

Blue argon lasers are used in surgery to weld arteries, destroy tumors, and correct eye defects.^[25]

Argon has also been used experimentally to replace nitrogen in the breathing or decompression mix known as Argox, to speed the elimination of dissolved nitrogen from the blood.^[49]

Lighting

 

Argon gas-discharge lamp forming the symbol for argon "Ar"

Incandescent lights are filled with argon, to preserve the filaments at high temperature from oxidation. It is used for the specific way it ionizes and emits light, such as in plasma globes and calorimetry in experimental particle physics. Gas-discharge lamps filled with pure argon provide lilac/violet light; with argon and some mercury, blue light. Argon is also used for blue and green argon-ion lasers.

Miscellaneous uses

Argon is used for thermal insulation in energy-efficient windows.^[50] Argon is also used in technical scuba diving to inflate a dry suit because it is inert and has low thermal conductivity.^[51]

Argon is used as a propellant in the development of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR). Compressed argon gas is allowed to expand, to cool the seeker heads of some versions of the AIM-9 Sidewinder missile and other missiles that use cooled thermal seeker heads. The gas is stored at high pressure.^[52]

Argon-39, with a half-life of 269 years, has been used for a number of applications, primarily ice core and ground water dating. Also, potassium–argon dating and related argon-argon dating are used to date sedimentary, metamorphic, and igneous rocks.^[25]

Argon has been used by athletes as a doping agent to simulate hypoxic conditions. In 2014, the World Anti-Doping Agency (WADA) added argon and xenon to the list of prohibited substances and methods, although at this time there is no reliable test for abuse.^[53]

Safety

Although argon is non-toxic, it is 38% more dense than air and therefore considered a dangerous asphyxiant in closed areas. It is difficult to detect because it is colorless, odorless, and tasteless. A 1994 incident, in which a man was asphyxiated after entering an argon-filled section of oil pipe under construction in Alaska, highlights the dangers of argon tank leakage in confined spaces and emphasizes the need for proper use, storage and handling.^[54]

See also

•  Chemistry portal

• Industrial gas
• Oxygen–argon ratio, a ratio of two physically similar gases, which has importance in various sectors.

References

1. "Standard Atomic Weights: Argon". CIAAW. 2017.
2. Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (4 May 2022). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
3. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.121. ISBN 1-4398-5511-0.
4. 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.
5. Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
6. Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
7. 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.
8. In older versions of the periodic table, the noble gases were identified as Group VIIIA or as Group 0. See Group (periodic table).
9. "Material Safety Data Sheet Gaseous Argon". UIGI.com. Universal Industrial Gases, Inc. Retrieved 14 October 2013.
10. Khriachtchev, Leonid; Pettersson, Mika; Runeberg, Nino; Lundell, Jan; et al. (2000). "A stable argon compound". Nature. 406 (6798): 874–876. Bibcode:2000Natur.406..874K. doi:10.1038/35022551. PMID 10972285. S2CID 4382128.
11. Perkins, S. (26 August 2000). "HArF! Argon's not so noble after all – researchers make argon fluorohydride". Science News.
12. Belosludov, V. R.; Subbotin, O. S.; Krupskii, D. S.; Prokuda, O. V.; et al. (2006). "Microscopic model of clathrate compounds". Journal of Physics: Conference Series. 29 (1): 1–7. Bibcode:2006JPhCS..29....1B. doi:10.1088/1742-6596/29/1/001.
13. Cohen, A.; Lundell, J.; Gerber, R. B. (2003). "First compounds with argon–carbon and argon–silicon chemical bonds". Journal of Chemical Physics. 119 (13): 6415. Bibcode:2003JChPh.119.6415C. doi:10.1063/1.1613631. S2CID 95850840.
14. Hiebert, E. N. (1963). "In Noble-Gas Compounds". In Hyman, H. H. (ed.). Historical Remarks on the Discovery of Argon: The First Noble Gas. University of Chicago Press. pp. 3–20.
15. Travers, M. W. (1928). The Discovery of the Rare Gases. Edward Arnold & Co. pp. 1–7.
16. Cavendish, Henry (1785). "Experiments on Air". Philosophical Transactions of the Royal Society. 75: 372–384. Bibcode:1785RSPT...75..372C. doi:10.1098/rstl.1785.0023.
17. Lord Rayleigh; Ramsay, William (1894–1895). "Argon, a New Constituent of the Atmosphere". Proceedings of the Royal Society. 57 (1): 265–287. doi:10.1098/rspl.1894.0149. JSTOR 115394.
18. Lord Rayleigh; Ramsay, William (1895). "VI. Argon: A New Constituent of the Atmosphere". Philosophical Transactions of the Royal Society A. 186: 187–241. Bibcode:1895RSPTA.186..187R. doi:10.1098/rsta.1895.0006. JSTOR 90645.
19. Ramsay, W. (1904). "Nobel Lecture". The Nobel Foundation.
20. "About Argon, the Inert; The New Element Supposedly Found in the Atmosphere". The New York Times. 3 March 1895. Retrieved 1 February 2009.
21. Emsley, John (2003). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. p. 36. ISBN 0198503407. Retrieved 12 June 2020.
22. Holden, N. E. (12 March 2004). "History of the Origin of the Chemical Elements and Their Discoverers". National Nuclear Data Center.
23. "Argon (Ar)". Encyclopædia Britannica. Retrieved 14 January 2014.
24. . Etacude.com. Archived from the original on 7 October 2008. Retrieved 8 March 2007.{{cite web}}: CS1 maint: unfit URL (link)
25. Emsley, J. (2001). Nature's Building Blocks. Oxford University Press. pp. 44–45. ISBN 978-0-19-960563-7.
26. . Archived from the original on 9 May 2007. Retrieved 7 March 2007.
27. Lodders, K. (2008). "The solar argon abundance". Astrophysical Journal. 674 (1): 607–611. arXiv:0710.4523. Bibcode:2008ApJ...674..607L. doi:10.1086/524725. S2CID 59150678.
28. Cameron, A. G. W. (1973). "Elemental and isotopic abundances of the volatile elements in the outer planets". Space Science Reviews. 14 (3–4): 392–400. Bibcode:1973SSRv...14..392C. doi:10.1007/BF00214750. S2CID 119861943.
29. Mahaffy, P. R.; Webster, C. R.; Atreya, S. K.; Franz, H.; Wong, M.; Conrad, P. G.; Harpold, D.; Jones, J. J.; Leshin, L. A.; Manning, H.; Owen, T.; Pepin, R. O.; Squyres, S.; Trainer, M.; Kemppinen, O.; Bridges, N.; Johnson, J. R.; Minitti, M.; Cremers, D.; Bell, J. F.; Edgar, L.; Farmer, J.; Godber, A.; Wadhwa, M.; Wellington, D.; McEwan, I.; Newman, C.; Richardson, M.; Charpentier, A.; et al. (2013). "Abundance and Isotopic Composition of Gases in the Martian Atmosphere from the Curiosity Rover". Science. 341 (6143): 263–6. Bibcode:2013Sci...341..263M. doi:10.1126/science.1237966. PMID 23869014. S2CID 206548973.
30. Young, Nigel A. (March 2013). "Main group coordination chemistry at low temperatures: A review of matrix isolated Group 12 to Group 18 complexes". Coordination Chemistry Reviews. 257 (5–6): 956–1010. doi:10.1016/j.ccr.2012.10.013.
31. Kean, Sam (2011). "Chemistry Way, Way Below Zero". The Disappearing Spoon. Black Bay Books.
32. Bartlett, Neil (8 September 2003). "The Noble Gases". Chemical & Engineering News. 81 (36): 32–34. doi:10.1021/cen-v081n036.p032.
33. Lockyear, JF; Douglas, K; Price, SD; Karwowska, M; et al. (2010). "Generation of the ArCF₂²⁺ Dication". Journal of Physical Chemistry Letters. 1: 358. doi:10.1021/jz900274p.
34. Barlow, M. J.; et al. (2013). "Detection of a Noble Gas Molecular Ion, ³⁶ArH⁺, in the Crab Nebula". Science. 342 (6164): 1343–1345. arXiv:1312.4843. Bibcode:2013Sci...342.1343B. doi:10.1126/science.1243582. PMID 24337290. S2CID 37578581.
35. Quenqua, Douglas (13 December 2013). "Noble Molecules Found in Space". The New York Times. Archived from the original on 1 January 2022. Retrieved 13 December 2013.
36. Kleppe, Annette K.; Amboage, Mónica; Jephcoat, Andrew P. (2014). "New high-pressure van der Waals compound Kr(H2)4 discovered in the krypton-hydrogen binary system". Scientific Reports. 4: 4989. Bibcode:2014NatSR...4E4989K. doi:10.1038/srep04989.
37. "Periodic Table of Elements: Argon – Ar". Environmentalchemistry.com. Retrieved 12 September 2008.
38. Fletcher, D. L. (PDF). Symposium: Recent Advances in Poultry Slaughter Technology. Archived from the original (PDF) on 24 July 2011. Retrieved 1 January 2010.
39. Shields, Sara J.; Raj, A. B. M. (2010). "A Critical Review of Electrical Water-Bath Stun Systems for Poultry Slaughter and Recent Developments in Alternative Technologies". Journal of Applied Animal Welfare Science. 13 (4): 281–299. CiteSeerX 10.1.1.680.5115. doi:10.1080/10888705.2010.507119. ISSN 1088-8705. PMID 20865613. S2CID 11301328.
40. Fraqueza, M. J.; Barreto, A. S. (2009). "The effect on turkey meat shelf life of modified-atmosphere packaging with an argon mixture". Poultry Science. 88 (9): 1991–1998. doi:10.3382/ps.2008-00239. ISSN 0032-5791. PMID 19687286.
41. Su, Joseph Z.; Kim, Andrew K.; Crampton, George P.; Liu, Zhigang (2001). "Fire Suppression with Inert Gas Agents". Journal of Fire Protection Engineering. 11 (2): 72–87. doi:10.1106/X21V-YQKU-PMKP-XGTP. ISSN 1042-3915.
42. Gastler, Dan; Kearns, Ed; Hime, Andrew; Stonehill, Laura C.; et al. (2012). "Measurement of scintillation efficiency for nuclear recoils in liquid argon". Physical Review C. 85 (6): 065811. arXiv:1004.0373. Bibcode:2012PhRvC..85f5811G. doi:10.1103/PhysRevC.85.065811. S2CID 6876533.
43. Xu, J.; Calaprice, F.; Galbiati, C.; Goretti, A.; Guray, G.; et al. (26 April 2012). "A Study of the Residual ³⁹
    Ar Content in Argon from Underground Sources". Astroparticle Physics. 66 (2015): 53–60. arXiv:1204.6011. Bibcode:2015APh....66...53X. doi:10.1016/j.astropartphys.2015.01.002. S2CID 117711599.
44. "Plasma electrons can be used to produce metallic films". Phys.org. 7 May 2020. Retrieved 8 May 2020.
45. Ilouga PE, Winkler D, Kirchhoff C, Schierholz B, Wölcke J (November 2007). "Investigation of 3 industry-wide applied storage conditions for compound libraries". Journal of Biomolecular Screening. 12 (1): 21–32. doi:10.1177/1087057106295507. PMID 17099243.
46. Zawalick, Steven Scott "Method for preserving an oxygen sensitive liquid product" U.S. patent 6,629,402 Issue date: 7 October 2003.
47. "Schedule for Renovation of the National Archives Building". Retrieved 7 July 2009.
48. "Fatal Gas Embolism Caused by Overpressurization during Laparoscopic Use of Argon Enhanced Coagulation". MDSR. 24 June 1994.
49. Pilmanis Andrew A.; Balldin U. I.; Webb James T.; Krause K. M. (2003). "Staged decompression to 3.5 psi using argon–oxygen and 100% oxygen breathing mixtures". Aviation, Space, and Environmental Medicine. 74 (12): 1243–1250. PMID 14692466.
50. "Energy-Efficient Windows". FineHomebuilding.com. February 1998. Retrieved 1 August 2009.
51. Nuckols M. L.; Giblo J.; Wood-Putnam J. L. (15–18 September 2008). . Proceedings of the Oceans 08 MTS/IEEE Quebec, Canada Meeting. Archived from the original on 21 July 2009. Retrieved 2 March 2009.{{cite journal}}: CS1 maint: unfit URL (link)
52. . planken.org. Archived from the original on 22 December 2008. Retrieved 1 February 2009.
53. . 31 August 2014. Archived from the original on 27 April 2021. Retrieved 1 September 2014.
54. Alaska FACE Investigation 94AK012 (23 June 1994). "Welder's Helper Asphyxiated in Argon-Inerted Pipe – Alaska (FACE AK-94-012)". State of Alaska Department of Public Health. Retrieved 29 January 2011.{{cite web}}: CS1 maint: numeric names: authors list (link)

Further reading

• Brown, T. L.; Bursten, B. E.; LeMay, H. E. (2006). J. Challice; N. Folchetti (eds.). Chemistry: The Central Science (10th ed.). Pearson Education. pp. 276& 289. ISBN 978-0-13-109686-8.
• Lide, D. R. (2005). "Properties of the Elements and Inorganic Compounds; Melting, boiling, triple, and critical temperatures of the elements". CRC Handbook of Chemistry and Physics (86th ed.). CRC Press. §4. ISBN 978-0-8493-0486-6. On triple point pressure at 69 kPa.
• Preston-Thomas, H. (1990). "The International Temperature Scale of 1990 (ITS-90)". Metrologia. 27 (1): 3–10. Bibcode:1990Metro..27....3P. doi:10.1088/0026-1394/27/1/002. S2CID 250785635. On triple point pressure at 83.8058 K.

External links

• Argon at The Periodic Table of Videos (University of Nottingham)
• USGS Periodic Table – Argon
• Diving applications: Why Argon?