Back to Elements
    Tl

    Thallium

    Post Transition

    Atomic Number: 81 • Atomic Mass: 204.3800 u • Period: 6 • Group: 13

    Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p¹
    Phase: Solid
    Electronegativity: 1.62
    Mercury (Hg)Lead (Pb)
    OverviewPropertiesAtomic StructureOccurrenceApplicationsHistory

    History

    Thallium has been known since ancient times

    Historical Timeline

    Discovered by spectroscopy

    Named for the bright green spectral line