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    IsotopeAtomic mass (Da)Isotopic abundance (amount fraction)
    120Te 119.904 06(2)0.0009(1)
    122Te 121.903 04(1)0.0255(12)
    123Te 122.904 27(1)0.0089(3)
    124Te 123.902 82(1)0.0474(14)
    125Te 124.904 43(1)0.0707(15)
    126Te 125.903 31(1)0.1884(25)
    128Te 127.904 461(6)0.3174(8)
    130Te 129.906 222 75(8)0.3408(62)

    In 1961, the Commission adopted Ar(Te) = 127.60 based on the chemical-ratio determinations. In the absence of calibrated mass-spectrometric measurements, the value of Ar(Te) = 127.60(3), adopted in 1969, has been retained as the standard atomic weight of tellurium.

    123Te, 128Te, and 130Te are radioactive; the minor isotope 123Te has a long half-life of 1.3(4)×1013 a and transforms into 123Sb without significantly affecting either element's atomic weight even over geological time. The major isotopes 128Te and 130Te have long half-lives of approximately 1024 a and 1021 a, respectively. These isotopes suffer double β– decay and are responsible for detectable xenon isotopic anomalies in old Te-bearing minerals.

    The "g" annotation for Te arises from the presence of naturally occurring fission products found in fossil reactors at Gabon, south-west Africa.

    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(Te) = 127.60(3) since 1969

    The name derives from the Latin Tellus, who was the Roman goddess of the Earth. Tellurium was discovered by Franz Joseph Müller von Reichenstein in 1782 and overlooked for 15 years until it was isolated by the German chemist Martin-Heinrich Klaproth in 1798. The Hungarian chemist Paul Kitaibel independently discovered tellurium in 1789, prior to Klaproth's work but after von Reichenstein.