A silvery-white, soft, ductile element of the lanthanide series occurring in the minerals monazite and bastnaesite and used to dope glass and plastics for lasers and to absorb neutrons in research. Europium oxides provide important phosphors for cathode-ray tubes and low-energy lighting applications. Atomic number 63; atomic weight 151.96; melting point 822°C; boiling point 1,596°C; specific gravity 5.244; valence 2, 3. See Periodic Table.