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    IsotopeAtomic mass (Da)Isotopic abundance (amount fraction)
    113In 112.904 062(6)0.042 81(52)
    115In 114.903 878 78(8)0.957 19(52)

    In 1991, the Commission changed the recommended value for the atomic weight of indium to Ar(In) = 114.818(3) based on high precision measurements of the metal and its compounds. The new measurement represents a significant improvement in the precision of the atomic weight and is in agreement with the previous values. The Commission revised the standard atomic weight of indium in 2011 in light of new mass-spectrometric measurements.

    115In is β– active with a half-life so long, 441(25)×1015 a, that it neither affects Ar(In) nor has it given rise to recognized abnormal occurrences of tin.

    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(In) = 114.818(1) since 2011

    The name derives from the term "indigo" for the indigo-blue line in the element's spark spectrum. It was discovered in 1863 by the German physicist Ferdinand Reich and the German metallurgist Hieronymus Theodor Richter, while examining zinc blende. They isolated indium in 1867.