NO. 034Reactive Nonmetal

Se

Selenium

Selenium is a Reactive Nonmetal with photoconductive properties and is essential in small amounts for living organisms.

Crystal Structure

Hexagonal

Atomic Mass78.97 u

Density4.81 g/cm³

Melting Point494 K

Boiling Point958 K

Atomic Radius103 pm

Electronegativity2.55

Ionization Energy941 kJ/mol

Electron Affinity195 kJ/mol

Bonding TypeCovalent

Oxidation States-2, 4, 6

Acid/BaseAcidic

ReactivityMedium

Electron Configuration

[Ar] 3d10 4s2 4p4

Discovered ByJöns Jakob Berzelius

Year1817

Known Isotopes

Se-74Se-76Se-77Se-78Se-80Se-82