In chemistry, the whole number rule states that the masses of the isotopes are whole number multiples of the mass of the hydrogen atom.[1] The rule is a modified version of Prout's hypothesis proposed in 1815, to the effect that atomic weights are multiples of the weight of the hydrogen atom.[2] It is also known as the Aston whole number rule[3] after Francis W. Aston who was awarded the Nobel Prize in Chemistry in 1922 "for his discovery, by means of his mass spectrograph, of isotopes, in a large number of non-radioactive elements, and for his enunciation of the whole-number rule."[4]
Francis W. Aston received the 1922 Nobel Prize in Chemistry for his enunciation of the whole-number rule.
The law of definite proportions was formulated by Joseph Proust around 1800[5] and states that all samples of a chemical compound will have the same elemental composition by mass. The atomic theory of John Dalton expanded this concept and explained matter as consisting of discrete atoms with one kind of atom for each element combined in fixed proportions to form compounds.[6]
Prout's hypothesisedit
In 1815, William Prout reported on his observation that the atomic weights of the elements were whole multiples of the atomic weight of hydrogen.[7][8] He then hypothesized that the hydrogen atom was the fundamental object and that the other elements were a combination of different numbers of hydrogen atoms.[9]
Aston's discovery of isotopesedit
In 1920, Francis W. Aston demonstrated through the use of a mass spectrometer that apparent deviations from Prout's hypothesis are predominantly due to the existence of isotopes.[10] For example, Aston discovered that neon has two isotopes with masses very close to 20 and 22 as per the whole number rule, and proposed that the non-integer value 20.2 for the atomic weight of neon is due to the fact that natural neon is a mixture of about 90% neon-20 and 10% neon-22). A secondary cause of deviations is the binding energy or mass defect of the individual isotopes.
During the 1920s, it was thought that the atomic nucleus was made of protons and electrons, which would account for the disparity between the atomic number of an atom and its atomic mass.[11][12] In 1932, James Chadwick discovered an uncharged particle of approximately the mass as the proton, which he called the neutron.[13] The fact that the atomic nucleus is composed of protons and neutrons was rapidly accepted and Chadwick was awarded the Nobel Prize in Physics in 1935 for his discovery.[14]
The modern form of the whole number rule is that the atomic mass of a given elemental isotope is approximately the mass number (number of protons plus neutrons) times an atomic mass unit (approximate mass of a proton, neutron, or hydrogen-1 atom). This rule predicts the atomic mass of nuclides and isotopes with an error of at most 1%, with most of the error explained by the mass deficit caused by nuclear binding energy.
Referencesedit
^Budzikiewicz H, Grigsby RD (2006). "Mass spectrometry and isotopes: a century of research and discussion". Mass Spectrometry Reviews. 25 (1): 146–57. Bibcode:2006MSRv...25..146B. doi:10.1002/mas.20061. PMID 16134128.
^Prout, William (1815). "On the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms". Annals of Philosophy. 6: 321–330. Retrieved 2007-09-08.
^Christopher G. Morris (1992). Academic Press Dictionary of Science and Technology. Gulf Professional Publishing. pp. 169–. ISBN978-0-12-200400-1.
^"The Nobel Prize in Chemistry 1922". nobelprize.org. The Nobel Foundation. 1922. Retrieved 2014-08-13.
^Proust, J.-L. (1799). Researches on copper, Ann. chim., 32:26-54. Excerpt, in Henry M. Leicester and Herbert S. Klickstein, A Source Book in Chemistry, 1400-1900, Cambridge, MA: Harvard, 1952. Accessed 2008-05-08.
^Dalton, J. (1808). A New System of Chemical Philosophy, volume 1, Manchester. Excerpt. Accessed 2008-05-08.
^William Prout (1815). On the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms. Annals of Philosophy, 6: 321–330. Online reprint
^William Prout (1816). Correction of a mistake in the essay on the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms. Annals of Philosophy, 7: 111–13. Online reprint
Harkins WD (1925). "The Separation of Chlorine into Isotopes (Isotopic Elements) and the Whole Number Rule for Atomic Weights". Proc. Natl. Acad. Sci. U.S.A. 11 (10): 624–8. Bibcode:1925PNAS...11..624H. doi:10.1073/pnas.11.10.624. PMC1086175. PMID 16587053.
External linksedit
1922 Nobel Prize Presentation Speech
January 01, 1970
whole, number, rule, chemistry, whole, number, rule, states, that, masses, isotopes, whole, number, multiples, mass, hydrogen, atom, rule, modified, version, prout, hypothesis, proposed, 1815, effect, that, atomic, weights, multiples, weight, hydrogen, atom, a. In chemistry the whole number rule states that the masses of the isotopes are whole number multiples of the mass of the hydrogen atom 1 The rule is a modified version of Prout s hypothesis proposed in 1815 to the effect that atomic weights are multiples of the weight of the hydrogen atom 2 It is also known as the Aston whole number rule 3 after Francis W Aston who was awarded the Nobel Prize in Chemistry in 1922 for his discovery by means of his mass spectrograph of isotopes in a large number of non radioactive elements and for his enunciation of the whole number rule 4 Francis W Aston received the 1922 Nobel Prize in Chemistry for his enunciation of the whole number rule Contents 1 Law of definite proportions 2 Prout s hypothesis 3 Aston s discovery of isotopes 4 Discovery of the neutron 5 References 6 Further reading 7 External linksLaw of definite proportions edit nbsp John Dalton s list of atomic weights and symbols The law of definite proportions was formulated by Joseph Proust around 1800 5 and states that all samples of a chemical compound will have the same elemental composition by mass The atomic theory of John Dalton expanded this concept and explained matter as consisting of discrete atoms with one kind of atom for each element combined in fixed proportions to form compounds 6 Prout s hypothesis editIn 1815 William Prout reported on his observation that the atomic weights of the elements were whole multiples of the atomic weight of hydrogen 7 8 He then hypothesized that the hydrogen atom was the fundamental object and that the other elements were a combination of different numbers of hydrogen atoms 9 Aston s discovery of isotopes editIn 1920 Francis W Aston demonstrated through the use of a mass spectrometer that apparent deviations from Prout s hypothesis are predominantly due to the existence of isotopes 10 For example Aston discovered that neon has two isotopes with masses very close to 20 and 22 as per the whole number rule and proposed that the non integer value 20 2 for the atomic weight of neon is due to the fact that natural neon is a mixture of about 90 neon 20 and 10 neon 22 A secondary cause of deviations is the binding energy or mass defect of the individual isotopes Discovery of the neutron editMain article Discovery of the neutron nbsp James Chadwick discoverer of the neutron with General Leslie Groves director of the Manhattan Project During the 1920s it was thought that the atomic nucleus was made of protons and electrons which would account for the disparity between the atomic number of an atom and its atomic mass 11 12 In 1932 James Chadwick discovered an uncharged particle of approximately the mass as the proton which he called the neutron 13 The fact that the atomic nucleus is composed of protons and neutrons was rapidly accepted and Chadwick was awarded the Nobel Prize in Physics in 1935 for his discovery 14 The modern form of the whole number rule is that the atomic mass of a given elemental isotope is approximately the mass number number of protons plus neutrons times an atomic mass unit approximate mass of a proton neutron or hydrogen 1 atom This rule predicts the atomic mass of nuclides and isotopes with an error of at most 1 with most of the error explained by the mass deficit caused by nuclear binding energy References edit Budzikiewicz H Grigsby RD 2006 Mass spectrometry and isotopes a century of research and discussion Mass Spectrometry Reviews 25 1 146 57 Bibcode 2006MSRv 25 146B doi 10 1002 mas 20061 PMID 16134128 Prout William 1815 On the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms Annals of Philosophy 6 321 330 Retrieved 2007 09 08 Christopher G Morris 1992 Academic Press Dictionary of Science and Technology Gulf Professional Publishing pp 169 ISBN 978 0 12 200400 1 The Nobel Prize in Chemistry 1922 nobelprize org The Nobel Foundation 1922 Retrieved 2014 08 13 Proust J L 1799 Researches on copper Ann chim 32 26 54 Excerpt in Henry M Leicester and Herbert S Klickstein A Source Book in Chemistry 1400 1900 Cambridge MA Harvard 1952 Accessed 2008 05 08 Dalton J 1808 A New System of Chemical Philosophy volume 1 Manchester Excerpt Accessed 2008 05 08 William Prout 1815 On the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms Annals of Philosophy 6 321 330 Online reprint William Prout 1816 Correction of a mistake in the essay on the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms Annals of Philosophy 7 111 13 Online reprint Lederman Leon 1993 The God Particle ISBN 9780385312110 Aston Francis W 1920 The constitution of atmospheric neon Philosophical Magazine 39 6 449 455 doi 10 1080 14786440408636058 Brown Laurie M 1978 The idea of the neutrino Physics Today 31 9 23 28 Bibcode 1978PhT 31i 23B doi 10 1063 1 2995181 Friedlander G Kennedy J W and Miller J M 1964 Nuclear and Radiochemistry 2nd edition Wiley pp 22 23 and 38 39 Chadwick James 1932 Possible Existence of a Neutron Nature 129 3252 312 Bibcode 1932Natur 129Q 312C doi 10 1038 129312a0 James Chadwick Biography The Nobel Foundation Retrieved 21 April 2013 Further reading editHarkins WD 1925 The Separation of Chlorine into Isotopes Isotopic Elements and the Whole Number Rule for Atomic Weights Proc Natl Acad Sci U S A 11 10 624 8 Bibcode 1925PNAS 11 624H doi 10 1073 pnas 11 10 624 PMC 1086175 PMID 16587053 External links edit1922 Nobel Prize Presentation Speech Retrieved from https en wikipedia org w index php title Whole number rule amp oldid 1182846716, wikipedia, wiki, book, books, library,
