< Highlights 84th Bureau - 44th Council - 85th Bureau
24 Aug 2007 14:45 Age: 7 year
Category: PAC, News from Divisions

Standard Atomic Weights Revised


The Commission on Isotopic Abundances and Atomic Weights (II.1) met in Pisa, Italy, prior the 44th IUPAC General Assembly held in Torino, Italy, 4-12 August 2007. Following its meeting, the Commission recommended significant changes to the standard atomic weights, Ar(E), of 5 chemical elements. The following changes are based on new determinations of isotopic abundances and reviews of previous isotopic abundances and atomic masses:

 

From

To

lutetium

174.967(1)

174.9668(1)

molybdenum

95.94(2)

95.96(2)

nickel

58.6934(2)

58.6934(4)

ytterbium

173.04(3)

173.054(5)

zinc

65.409(4)

65.38(2)

The values are presented in a concise notation whereby the standard uncertainty is given in parenthesis next to the least significant digits to which it applies; for example, Ar(Zn) = 65.38(2) is the concise form of the expression Ar(Zn) = 65.38 0.02

In addition, the recommended value for the isotope amount ratio of 40Ar/36Ar, which may be of importance to geochronologists, has been changed from 296.03(53) to 298.56(31).

These changes will be published in a new Table of Standard Atomic Weights 2007, which will be submitted for publication in Pure and Applied Chemistry by the end of 2007. For more details about the Commission, see www.iupac.org/divisions/II/II.1, or contact Michael E. Wieser (mwieser@ucalgary.ca), secretary of the Commission.