A group of metallic elements having closesly similar chemical properties. They are mainly trivalent, but otherwise similar to the alkaline earth elements. The group consists of the lanthanide elements with atomic numbers 57 (lanthanum) to 71, plus scandium (21) and yttrium (39).
Elements with atomic numbers 57 (Lanthanum) to 71 (Lutetium) inclusive plus scandium and yttrium.
Synonym for lanthanides ... Those elements with atomic numbers 57-71 which closely resemble one another chemically and were once difficult to separate from one another. ... Synonym: rare earth elements. ... Origin: Lanthanum, first element of the series ... (05 Mar 2000) ... 
Type: Term Synonyms: lanthanides
Relatively scarce minerals such as niobium and yttrium.