Rareearth element Wikipedia
A rareearth element (REE) or rareearth metal (REM), as defined by the International Union of Pure and Applied Chemistry, is one of a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides, as well as scandium and yttrium. Scandium and yttrium are considered rareearth elements because they tend to occur in the same ore deposits as the lanthanides and ...