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    Ac

    Actinium

    Actinide

    Atomic Number: 89 • Atomic Mass: 227.0000 u • Period: 7 • Group: 3

    Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 6d¹
    Phase: Solid
    Electronegativity: 1.1
    Radium (Ra)Thorium (Th)
    OverviewPropertiesAtomic StructureOccurrenceApplicationsHistory

    Occurrence

    Actinium is found in various natural sources, including minerals, rocks, and the Earth's crust.

    • Trace amounts in uranium ores
    • Less than 0.001 parts per million in Earth's crust
    • Primarily from the decay of uranium-235