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    IsotopeAtomic mass (Da)Isotopic abundance (amount fraction)
    75As 74.921 595(6)1

    Arsenic is a monoisotopic element and its atomic weight is determined solely by its isotope 75As. The Commission last revised the standard atomic weight of arsenic in 2013 based on the latest Atomic Mass Evaluation by IUPAP.

    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(As) = 74.921 595(6) since 2013

    The name derives from the Latin arsenicium and the Greek arsenikos for "masculine" or "male" because the ancients thought that metals were different sexes. Arsenic was known in prehistoric times for its poisonous sulfides. The German scientist and philosopher, Albert von Bollstadt (Albert the Great or Albertus Magnus) is thought to have obtained the metal around 1250.