Energy level diagram

• Er-O-Ti
• Al-Ce-O-Y-Yb
• Al-Ce-O-Y
• Al-La-O-Sr-Ta-Yb
• Br-Fe-Th
• transitional
• chalcogen
• nonmetal
• lanthanoid
• rare earth
• cubic
• monoclinic
• tetragonal
• trigonal
• orthorhombic