A
rare earth element (
REE) or
rare earth metal (
REM), as defined by
IUPAC, 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 rare earth elements because they tend to occur in the same
ore deposits as the lanthanides and exhibit similar chemical properties.