News & Notices
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:
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 ±
In addition, the recommended value for the isotope amount ratio of
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.
secretary of the Commission.
first posted 23 August
published in Chem. Int. Nov 2007>
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