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Lanthanide contraction

    Lanthanide contraction is a term used by various sources to explain different but closely related concepts

    Concept #1

    Lanthanide contraction is a phenomenon where the atomic radii of elements in the lanthanide series (Z=58 to 71) are smaller than would normally be expected Since electrons in an f subshell poorly screen electrons from the nucleus the outer-shell electrons are held more tightly; this results in a smaller atomic radii
    Technical reference page

    Concept #2

    Generally the lanthanide contraction is used as a partial explanation for why the third transition series have only marginally larger atomic radii than the second transition series This is due to the the f orbitals been poorly shielding but this does not cause a major abnormality in the atomic radii of the lanthanides themselves
    Reference Page See Figure 2 for details

    Concept #3

    Lanthanide contraction describes a decrease in the radii of the elements following the lanthanides compared to what would be expected if there were no f-transition metals
    Simple Definition