Oxygen
Oxygen (氧, symbol O) is chemical element number 8, a Reactive Nonmetal in period 2, group 16 of the periodic table, with a standard atomic weight of about 15.999. Essential for cellular respiration. Third most abundant element in the universe.
Properties
| Atomic number | 8 |
|---|---|
| Symbol | O |
| Atomic mass | 15.999 u |
| Category | Reactive Nonmetal |
| Period | 2 |
| Group | 16 |
| Electron configuration | [He] 2s² 2p⁴ |
| Electronegativity | 3.44 |
| Covalent radius | 66 pm |
| Density | 0.001429 g/cm³ |
| Melting point | 54.36 K |
| Boiling point | 90.2 K |
| Discovery | Carl W. Scheele, 1771 |
Overview
Essential for cellular respiration. Third most abundant element in the universe. Oxygen (symbol O) is chemical element number 8, sitting in period 2, group 16 of the periodic table and classed as a Reactive Nonmetal. As a nonmetal it tends to gain electrons, or to share them with other nonmetals when bonding.
Its electron configuration is [He] 2s² 2p⁴, with 6 electrons in the outer shell, and an electronegativity of about 3.44 (Pauling). Around 25 °C it is usually a gas (a very low melting point); it melts near 54.36 K (-218.8 °C), boils near 90.2 K (-182.9 °C), has a density around 0.001429 g/cm³.
In industry and daily life it turns up in Industrial Gas and Medical / Pharma. You can explore O-containing compounds here such as H₂SO₄, HNO₃ and CH₃COOH. It is regarded as a moderate-hazard element, so handle it with appropriate care. It was first described by Carl W. Scheele in 1771. Use the comparison tool to line it up against other elements.
Electron shells
Electrons per shell: 2 · 6
Main uses
- Industrial Gas
- Medical / Pharma
Hazard
Compounds containing Oxygen
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.