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    IsotopeAtomic mass (Da)Isotopic abundance (amount fraction)
    70Ge 69.924 249(6)0.2052(19)
    72Ge 71.922 0758(5)0.2745(15)
    73Ge 72.923 4590(4)0.0776(8)
    74Ge 73.921 177 76(9)0.3652(12)
    76Ge 75.921 4027(2)0.0775(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.

    SOURCE  Atomic weights of the elements: Review 2000 by John R de Laeter et al. Pure Appl. Chem. 2003 (75) 683-800
    © IUPAC 2003


    Ar(Ge) = 72.630(8) since 2011

    The name derives from the Latin germania for Germany. It was discovered and isolated by the German chemist Clemens-Alexander Winkler in 1886 in the mineral argyrodite (GeS2×4Ag2S).

    Isotopic reference materials of germanium.