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Vol. 27 No. 6
November-December 2005

IUPAC Wire | News and information on IUPAC, its fellows, and members organizations
See also www.iupac.org/news

Standard Atomic Weights Revised

Following its meeting, held 10-11 August 2005 at the 43rd IUPAC General Assembly, the Commission on Isotopic Abundances and Atomic Weights (II.1) released the changes to the standard atomic weights of 16 chemical elements. The following changes are based on new determinations of isotopic abundances and reviews of previous isotopic abundances and atomic masses:

  From To
Aluminium 26.981 538 (2) 26.981 5386 (8)
Bismuth 208.980 38 (2) 208.980 40 (1)
Caesium 132.905 45 (2) 132.905 4519 (2)
Cobalt 58.933 200 (9) 58.933 195 (5)
Gold 196.966 55 (2) 196.966 569 (4)
Lanthanum 138.9055 (2)   138.905 47 (7)  
Manganese 54.938 049 (9) 54.938 045 (5)
Neodymium   144.24 (3)   144.242 (3)  
Phosphorus 30.973 761 (2) 30.973 762 (2)
Platinum 195.078 (2) 195.084 (9)
Samarium 150.36 (3) 150.36 (2)
Scandium 44.955 910 (8) 44.955 912 (6)
Sodium 22.989 770 (2) 22.989 769 28 (2)
Tantalum 180.9479 (1) 180.947 88 (2)
Terbium 158.925 34 (2)   158.925 35 (2)
Thorium 232.0381 (1)   232.038 06 (2)

These changes in the atomic weights will be published in a new Table of Standard Atomic Weights 2005, which will be submitted for publication in Pure and Applied Chemistry* by the end of 2005. The commission also continued its review of publications of variations in the natural isotopic abundances. The commission also continued its review of publications of the variation in the natural isotopic abundances. For more details about the Commission meeting in Beijing, see Division Roundups (in print on page 7).

For more information, contact Michael E. Wieser <mwieser@ucalgary.ca>, secretary of the IUPAC Commission on Isotopic Abundances and Atomic Weights.

 

* IUPAC Technical Report as Pure Appl. Chem. 78(11), 2051-2066, 2006


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