Energy level diagram, Lanthanoid, Nonmetal, Rare earth, Transitional

• Er-O-Y-Yb
• Er-La-O-V-Yb
• Al-Ce-O-Y
• Er-O-V-Y-Yb
• Er-O-Ti
• rare earth
• transitional
• lanthanoid
• nonmetal
• chalcogen
• tetragonal
• cubic
• monoclinic
• orthorhombic
• trigonal