any of the rare-earth elements (lanthanide series)
sometimes called lan′tha·noid· or lan′tha·non·
Any of a series of chemically similar metallic elements with atomic numbers ranging from 57 (lanthanum) through 71 (lutetium). The lanthanides, together with yttrium and scandium, constitute the rare-earth elements. Also called lanthanoid .
Origin of lanthanidelanthan(um) -ide
- According to IUPAC - "Although lanthanoid means 'like lanthanum' and so should not include lanthanum, lanthanum has become included by common usage. Similarly, actinoid. The ending 'ide' normally indicates a negative ion, and therefore lanthanoid and actinoid are preferred to lanthanide and actinide. However, lanthanide and actinide are still allowed owing to wide current use."