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Pronunciation: lan'tha-nidz

Definition: Those elements with atomic numbers 57–71 that closely resemble one another chemically and were formerly difficult to separate from one another. they vary in the electrons in the 4f orbital.

Synonym(s): rare earth elements

[lanthanum, first element of the series]

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review Date: Sep 19, 2016.