|Isotope||Atomic mass (Da)||Isotopic abundance (amount fraction)|
|74Ge||73.921 177 76(9)||0.3652(12)|
In 1961, the Commission recommended Ar(Ge) = 72.59, based on chemical ratio determinations. At that time it was also noted that the available mass-spectrometric measurements averaged to Ar(Ge) = 72.628, which conflicted with the accepted chemical values. In 1983, the Commission recalculated the chemical determinations based on current values of the atomic weights of all other elements. Assigning equal weight to these determinations yielded an Ar(Ge) = 72.592. Equating the density of the structural crystal cell of elemental germanium with the macroscopic density gives Ar(Ge) = 72.63, in accord with the mass-spectrometric value.
In 1985, following a new measurement of the isotopic composition, the Commission re-examined the value for the atomic weight and recommended a higher value of Ar(Ge) = 72.61(2). It also noted that there was still concern over the discrepancy between the chemical value and that determined by mass spectrometry, but while not wishing to discard the chemical work favoured the mass-spectrometric value.
In 1999, two new measurements of the isotopic composition of germanium yielded values of 72.6276(32) and 72.639(7) for the atomic weight. The discrepancy between these results was resolved in 2011 when new measurements confirmed the lower value.
© IUPAC 2003