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    Strontium

    IsotopeAtomic mass (Da)Isotopic abundance (amount fraction)
    84Sr 83.913 419(8)0.0056(2)
    86Sr 85.909 261(8)0.0986(20)
    87Sr 86.908 878(8)0.0700(20)
    88Sr 87.905 613(8)0.8258(35)

    In its 1961 report, the Commission recommended Ar(Sr) = 87.62 based on the mass-spectrometric determination of Nier. This value was revised to Ar(Sr) = 87.62(1) in 1969 and it remains unchanged since.

    Known natural variations in the abundance of 87Sr, the product isotope of radioactive 87Rb decay, prevent the recommendation of a more precise standard atomic-weight value. The n(87Sr)/n(86Sr) ratio is a convenient measure of that variability. Anomalous traces of almost pure 87Sr have been reported from rubidium ores, for which the atomic weight will not be in the tabulated standard atomic weight range.

    The appreciable variability in n(87Sr)/n(86Sr) is the basis for Rb-Sr geochronology, and for analysis of source components in mixtures of water and geologic materials.

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

    CIAAW

    Strontium
    Ar(Sr) = 87.62(1) since 1969

    The name derives from Strontian, a town in Scotland. The mineral strontianite is found in mines in Strontian. The element was discovered in 1792 by the Scottish chemist and physician Thomas Charles Hope, who observed the brilliant red flame colour of strontium. It was first isolated by the English chemist Humphry Davy in 1808.

    Isotopic reference materials of strontium.