Atomic number 34
Name Selenium
Atomic mass 78.96(3)
Electronic configuration [Ar] 3d10 4s2 4p4
Electronegativity 2.55
Atomic radius 116 pm
Ion radius 198 (-2) pm
Van der Waals radius 190 pm
Ionization energy 941 kJ/mol
Electron affinity -195 kJ/mol
Oxidation states -2, 2, 4, 6
Standard physical state solid
Bonding type metallic
Melting point 494 °C
Boiling point 958 °C
Density 4.819 g/cm³
Type nonmetal
Year discovered 1817