|Isotope||Atomic mass (Da)||Isotopic abundance (amount fraction)|
|107Ag||106.905 09(2)||0.518 39(8)|
|109Ag||108.904 755(9)||0.481 61(8)|
In its 1961 report, the Commission recommended Ar(Ag) = 107.870(3) after carefully reviewing the reliability of this value. It was recognized to be of great importance because some forty other elements had their atomic weights determined in terms of the equivalence of their halides to silver or silver halides. In 1967, new atomic-weight-value for bromine prompted revisions of the atomic weights of chlorine and silver; Ar(Ag) was changed to a value of 107.868(1).
In 1981, the Commission welcomed a superior new isotope-abundance measurement by NIST. No significant difference was found between a number of silver metal and mineral samples with one minor exception now believed to be due to an impurity. The Commission was able to recommend Ar(Ag) = 107.8682(3), which was revised slightly in 1985.
Through the greater use of mass-spectrometric determinations of atomic weights, silver is losing some of its key role attributable to the stability of its monovalent ion. However, the atomic weight of silver has lost none of its significance as a principal means for determining the Faraday constant. The atomic weight determination coupled with the best value of the electrochemical equivalent of silver, has re-established the electrochemical method as the most accurate for determining the Faraday constant, and has significantly contributed to least squares adjustments of the fundamental constants.
© IUPAC 2003