Element 34
Selenium (Se)
Selenium (Se) is element 34 of the periodic table, a reactive nonmetal in period 4, group 16 (p-block) with an atomic mass of 78.971 and is a solid at standard conditions.
At a glance
- Atomic number
- 34
- Symbol
- Se
- Atomic mass
- 78.971 u
- Category
- Reactive nonmetals
- Period
- 4
- Group
- 16
- Block
- p-block
- Phase at STP
- solid
Electron structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4
- Shorthand configuration
- [Ar] 3d10 4s2 4p4
- Electrons per shell
- 2, 8, 18, 6
- Oxidation states
- -2, -1, +1, +2, +3, +4, +5, +6
Physical properties
- Melting point
- 494 K
- Boiling point
- 958 K
- Density
- 4.809 g/cm3
- Phase
- solid
Atomic properties
- Electronegativity (Pauling)
- 2.55
- Atomic radius
- 103 pm
- Covalent radius
- 120 pm
- Van der Waals radius
- 190 pm
- First ionization energy
- 941 kJ/mol
- Electron affinity
- 195 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| Se-80 | 79.91652 | 49.61% | Stable |
Common uses
- Glass making
- Electronics
- Solar cells
- Supplements
Discovery
- Year
- 1817
- Discovered by
- Jöns Jacob Berzelius
- Country
- Sweden