Selenium
Reactive Nonmetal
Selenium (Se) is a chemical element with atomic number 34, classified as a reactive nonmetal. At room temperature it is a solid. It was discovered in 1817 by Jöns Jacob Berzelius.
Properties
- Atomic number
- 34
- Atomic mass
- 78.971 u
- Category
- Reactive Nonmetal
- Group
- 16
- Period
- 4
- Block
- p-block
- Electron configuration
- [Ar] 3d¹⁰ 4s² 4p⁴
- Phase at STP
- Solid
- Density
- 4.809 g/cm³
- Melting point
- 494 K (220.9 °C)
- Boiling point
- 958 K (684.9 °C)
- Electronegativity
- 2.55
- Atomic radius
- 103 pm
- Ionization energy
- 9.752 eV
- Discovery
- 1817 · Jöns Jacob Berzelius
Common uses
Glass manufacturing, photocopiers, solar cells, supplements
Did you know?
Essential trace element for humans and conducts electricity when exposed to light.
Experiment with the elements
Selenium doesn't form any compounds in our lab yet, but the periodic table sandbox lets you combine dozens of other real elements into real compounds — water, table salt, ammonia and many more — with their true chemical formulas.