Selenium
Selenium (硒, symbol Se) is chemical element number 34, a Reactive Nonmetal in period 4, group 16 of the periodic table, with a standard atomic weight of about 78.971. Nonmetal with photovoltaic properties. Essential trace element in many enzymes.
Properties
| Atomic number | 34 |
|---|---|
| Symbol | Se |
| Atomic mass | 78.971 u |
| Category | Reactive Nonmetal |
| Period | 4 |
| Group | 16 |
| Electron configuration | [Ar] 3d¹⁰ 4s² 4p⁴ |
| Electronegativity | 2.55 |
| Covalent radius | 120 pm |
| Density | 4.809 g/cm³ |
| Melting point | 453 K |
| Boiling point | 958 K |
| Discovery | Jöns Jakob Berzelius, 1817 |
Overview
Nonmetal with photovoltaic properties. Essential trace element in many enzymes. Selenium (Se) is a Reactive Nonmetal with atomic number 34, located in period 4, group 16. As a nonmetal it tends to gain electrons, or to share them with other nonmetals when bonding.
With 6 electrons in its outermost shell, Selenium bonds accordingly; full configuration [Ar] 3d¹⁰ 4s² 4p⁴, electronegativity 2.55. At room temperature it is normally a solid; it melts near 453 K (179.9 °C), boils near 958 K (684.9 °C), has a density around 4.809 g/cm³.
Common applications range across Electronics / Semiconductors, Medical / Pharma and Pigments / Glass. It is regarded as a moderate-hazard element, so handle it with appropriate care. It was first described by Jöns Jakob Berzelius in 1817. The periodic trends guide explains the underlying patterns.
Electron shells
Electrons per shell: 2 · 8 · 18 · 6
Main uses
- Electronics / Semiconductors
- Medical / Pharma
- Pigments / Glass
Hazard
Compounds containing Selenium
No compounds in this knowledge base contain Selenium yet.
Data sources
Atomic mass uses IUPAC (CIAAW) standard atomic weights; the covalent radius is from Cordero et al. (2008). Verify on the RSC Periodic Table, PubChem and Wikipedia. Educational reference only.