34Solid
Se 78.96 Atomic mass · uNonmetals
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.
Discovery 1817 (Jöns Jakob Berzelius)
K2L8M18N6
Physical properties
Values for the element in its standard state.
- Density
- 4.819g/cm³
- Melting point
- 494K
- Boiling point
- 958K
- Atomic radius
- 116pm
- Bonding type
- Metallic
- Molar heat
- 25.363J/(mol·K)
Inside the atom
Electron arrangement and the energy behind its behavior.
Full electron configuration
1s, 2 electrons; 2s, 2 electrons; 2p, 6 electrons; 3s, 2 electrons; 3p, 6 electrons; 3d, 10 electrons; 4s, 2 electrons; 4p, 4 electrons;
[Ar] represents 18 core electrons. The full view shows them explicitly.
34 electrons Orbital order preserved from source
- Electronegativity
- 2.55Pauling scale
- First ionization energy
- 941kJ/mol
- Electron affinity
- 195kJ/mol
- Van der Waals radius
- 190pm
Se SeleniumAtomic number 34
941kJ/mol
Atomic numberGaps indicate unavailable data
About selenium
- Appearance
- Black, red, and gray (not pictured) allotropes
- Discovery
- 1817 (Jöns Jakob Berzelius)
- Data source
- Read the reference
A missing value means it is unavailable in this reference dataset. Values can vary with measurement method and conditions.