34 Se 78.972
Selenium
polyatomic nonmetal
Properties
- Atomic number
- 34
- Atomic mass
- 78.972 u
- Category
- polyatomic nonmetal
- Group
- 16
- Period
- 4
- Block
- p-block
- State (room temp)
- Solid
- Outer-shell electrons
- 6
- Electronegativity
- 2.55 (Pauling)
- Density
- 4.81 g/cm³
- Melting point
- 220.85 °C
- Boiling point
- 684.85 °C
Electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴
Noble-gas shorthand: [Ar] 3d¹⁰ 4s² 4p⁴
Electrons per shell: 2, 8, 18, 6 — that's 6 in the outermost shell.
About Selenium
Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between those of its periodic table column-adjacent chalcogen elements sulfur and tellurium. It rarely occurs in its elemental state in nature, or as pure ore compounds.
- Discovered by Jöns Jakob Berzelius
- Appearance: black, red, and gray (not pictured) allotropes
Position in the periodic table
Data compiled from Wikipedia, PubChem, and IUPAC. Source.