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    Pm

    Promethium

    Lanthanide

    Atomic Number: 61 • Atomic Mass: 145.0000 u • Period: 6 • Group: 101

    Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁵
    Phase: Solid
    Electronegativity: 1.13
    Neodymium (Nd)Samarium (Sm)
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    History

    Promethium has been known since ancient times

    Historical Timeline

    Created in nuclear reactions

    Identified from nuclear reactor fuel