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lanthanide
Any member of a group of rare, metallic elements with atomic numbers from 57 (lanthanum) to 71 (lutetium) inclusive, in which the 4f orbitals are being filled. The lanthanides are: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The properties of these metals are all very similar and resemble those of aluminum.
The lanthanides are separated by chromatography and ion-exchange resins. They are used in alloys, including misch metal; and their compounds (mixed or separately) are used as abrasives, for making glasses and ceramics, as "getters," as catalysts in the petroleum industry, and to make phosphors, lasers, and microwave devices.
Except for promethium, the lanthanides are not uncommon – the normal source is monazite which contains 90% La, Ce, Pr, Nd in its lanthanide contents.
See also rare earth elements.
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• INORGANIC CHEMISTRY
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