lanthanide contraction


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lanthanide contraction

[′lan·thə‚nīd kən‚trak·shən]
(atomic physics)
A phenomenon encountered in the rare-earth elements; the radii of the atoms of the members of the series decrease slightly as the atomic numbers increase; starting with element 58 in the periodic table, the balancing electron fills in an inner incomplete 4ƒ shell as the charge on the nucleus increases.
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