8OOxygen15.999[He] 2s² 2p⁴
diatomic nonmetal
Oxygen
Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table and is a highly reactive nonmetal and oxidizing agent that readily forms compounds (notably oxides) with most elements. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
Electrons by shell
Electron configuration
2s2
2p4
At a glance
- Atomic number
- 8
- Atomic mass
- 15.999 u
- Phase
- Gas
- Density
- 1.429 g/L
- Melting point
- 54.36 K
- Boiling point
- 90.188 K
- First ionization energy
- 1,313.9 kJ/mol
- Electronegativity
- 3.44
- Electron affinity
- 140.976 kJ/mol
- Molar heat capacity
- Unavailable
- Period
- 2
- Appearance
- Unavailable
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.