出典:Wikipedia
出典:『Wikipedia』 (2011/05/31 23:05 UTC 版)
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanoids plus scandium and yttrium. Scandium and yttrium are considered rare earth elements since they tend to occur in the same ore deposits as the lanthanoids and exhibit similar chemical properties.