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    Se

    Selenium

    Nonmetal

    Atomic Number: 34 • Atomic Mass: 78.9710 u • Period: 4 • Group: 16

    Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴
    Phase: Solid
    Electronegativity: 2.55
    Arsenic (As)Bromine (Br)
    OverviewPropertiesAtomic StructureOccurrenceApplicationsHistory

    History

    Selenium has been known since ancient times

    Historical Timeline

    Discovered during the production of sulfuric acid

    Initially thought to be tellurium

    Named after the moon (as tellurium was named after Earth)