Oxygen (O)
Oxygen (O) is element 8, a nonmetal. Atomic mass 15.999, configuration [He] 2s² 2p⁴. Properties, isotopes, oxidation states, uses and history, with an interactive 3D atom model.
Key facts
| Atomic number | 8 |
|---|---|
| Symbol | O |
| Standard atomic weight | [15.99903,15.99977] |
| Category | Other nonmetal |
| Group | 16 |
| Period | 2 |
| State at room temperature | Gas |
| Electron configuration | [He] 2s² 2p⁴ |
| Valence electrons | 6 |
| Common oxidation states | -2 |
| Common ions | O²⁻ |
| Electronegativity (Pauling) | 3.44 |
| First ionization energy | 1314 kJ/mol |
| Electron affinity | 141 kJ/mol |
| Atomic radius | 48 pm |
| Density | 1.308 g/L |
| Melting point | -218.78°C |
| Boiling point | -182.9°C |
| Specific heat | 0.918 J/(g·°C) |
Natural isotopes
- O-16: Stable (99.76%)
- O-17: Stable (0.04%)
- O-18: Stable (0.20%)
Common uses
- Steel making
- Medical life support
- Water treatment
Where it matters
- Biological respiration
- Combustion engines
- Ozone layer protection
Hazards
- Oxidizer (accelerates fire)
History
| Discovered | 1774 |
|---|---|
| Discovered by | Joseph Priestley / Carl Wilhelm Scheele |
| Name | Antoine Lavoisier |