Chalcogen, Rare earth, Energy level diagram

• Er-O-Ti
• Al-Ce-O-Y
• Ba-Ce-Cl-Eu-O-P
• Al-Ce-O-Y-Yb
• Al-La-O-Sr-Ta-Yb
• chalcogen
• lanthanoid
• rare earth
• nonmetal
• transitional
• cubic
• tetragonal
• monoclinic
• orthorhombic
• trigonal