Logo of the Atomic Weights Commission Logo of the International Union of Pure and Applied Chemistry


    IsotopeAtomic mass (Da)Isotopic abundance (amount fraction)
    165Ho 164.930 329(5)1

    Holmium is a monoisotopic element and its atomic weight is determined solely by its isotope 165Ho. The Commission last revised the standard atomic weight of holmium in 2021 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(Ho) = 164.930 329(5) since 2021

    The name derives from the Latin holmia for Stockholm. It was discovered in erbia earth by the Swiss chemist J. L. Soret in 1878, who referred to it as element X. It was later independently discovered by the Swedish chemist Per Theodor Cleve in 1879. It was first isolated in 1911 by Homberg, who proposed the name holmium either to recognize the discoverer Per Cleve, who was from Stockholm, or perhaps to establish his own name in history.