Chemical Sciences: A Manual for CSIR-UGC National Eligibility Test for Lectureship and JRF/Whole number rule

The Whole Number Rule states that the masses of the elements are whole number multiples of the mass of the hydrogen atom.Budzikiewicz H, Grigsby RD Mass spectrometry and isotopes: a century of research and discussion Mass spectrometry reviews 25 1 146–57 2006 16134128 10.1002/mas.20061 The rule can be formulated from Prout's hypothesis put forth in 1815. On the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms. Annals of Philosophy 1815 William Prout 6 321–330 http://web.lemoyne.edu/~giunta/PROUT.HTML 2007-09-08 In 1920, Francis W. Aston demonstrated through the use of a mass spectrometer that apparent deviations from the rule are predominantly due to the existence of isotopes; The constitution of atmospheric neon Philosophical Magazine 1920 Francis W. Aston 39 6 449–455 2007-09-08 they are secondarily due to binding energy, as mass defect. The modern form of the whole number rule is that the atomic mass of a given 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). References Harkins WD 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 1925 16587053 10.1073/pnas.11.10.624 1086175