Number: 1999-043-1-200 [ 990431/200/00 ]
Title: Element by Element Review of Atomic Weights to the Year
2000
Task Group
Chairman: J.R.
de Laeter
Members: J.K.
Bohlke, P. De Bi�vre,
H. Hidaka, H.S.
Peiser, K.J.R. Rosman,
P. Taylor
Completion Date: 2002 - project completed
Objective:
A Review article of the science of atomic weights.
Description:
The review describes the information on the isotopic compositions
and atomic weights of the elements as evaluated regularly by the Commission
on Atomic Weights and Isotopic Abundances.
The Review aims:
(i) to describe the developments in atomic weights determinations
during the 20th Century.
(ii) to give current best values of the atomic weights and isotope
abundances of each element with their associated uncertainties;
(iii) the literature sources of these values and
(iv) the known limitations to the applicability of these values.
A consistent set of internationally accepted atomic weights has long
been an essential aim of the scientific community because of the relevance
of these values to science and technology, as well as to trade and commerce
subject to moral, legal and international standards. Relative atomic
weights were originally determined by elemental mass measurements coupled
with an understanding of chemical stoichiometry, but are now based almost
entirely on a knowledge of the isotopic composition and the atomic masses
of the isotopes of the elements. Atomic weights and atomic masses are
now scaled so that the numeric values for the carbon isotope of mass
12 is 12 exactly, and these quantities are invariably associated with
carefully defined, estimated uncertainties.
This review reflects the current and increasing interest of science
in the measured differences between source-specific and even sample-specific
atomic weights. These relative comparisons can often be made with a
smaller uncertainty that is achieved in the best calibrated atomic-weight
determinations. As well as unequivocally determining the origin of chemical
compounds, accurate determinations of the atomic weights of certain
elements also effect the values of a number of fundamental constants.
Progress:
A subset of the writing group will be meeting in mid-June, in Belgium,
to finalize the manuscript. Publication in PAC and annoncement
in CI will follow.
Project completed - IUPAC Technical Report published in Pure
Appl. Chem. 75(6),
683-799, 2003.
Last update: 10 June 2003