Back to Elements
    Tm

    Thulium

    Lanthanide

    Atomic Number: 69 • Atomic Mass: 168.9300 u • Period: 6 • Group: 101

    Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹³
    Phase: Solid
    Electronegativity: 1.25
    Erbium (Er)Ytterbium (Yb)
    OverviewPropertiesAtomic StructureOccurrenceApplicationsHistory

    Physical & Chemical Properties

    Physical Properties

    • •Silvery-gray metal
    • •Soft and malleable
    • •Can be cut with a knife
    Melting Point

    1818 K (1544.85 °C, 2812.73 °F)

    Boiling Point

    2223 K (1949.85 °C, 3541.73 °F)

    Density

    9.321 g/cm³

    Electronegativity

    1.25 (Pauling scale)

    Chemical Properties

    • •Forms trivalent compounds
    • •Oxidizes slowly in air
    • •Reacts with dilute acids

    Electron Configuration

    1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹³

    Electron configuration describes how electrons are distributed in atomic orbitals, showing how they are arranged in energy levels and subshells.