Number of Isotopes: 2 Electron Affinity (kJ/mol): 30 First Ionization Energy (kJ/mol): 558.3 Second Ionization Energy (kJ/mol): 1820.6 Third Ionization Energy (kJ/mol): 2704.5 Electronegativity: 1.78 Polarizability (Å3): 9.7 Atomic Volume (cm3/mol): 15.7 Ionic Radius2- (pm): No data Ionic Radius1- (pm): No data Atomic Radius (pm): 167 Ionic Radius1+ (pm): No data Ionic Radius2+ (pm): No data Ionic Radius3+ (pm): 94 Common Oxidation Numbers: +3 Other Oxid. Numbers: +1, +2