Element 8
Oxygen (O)
Oxygen (O) is element 8 of the periodic table, a reactive nonmetal in period 2, group 16 (p-block) with an atomic mass of 15.999 and is a gas at standard conditions.
At a glance
- Atomic number
- 8
- Symbol
- O
- Atomic mass
- 15.999 u
- Category
- Reactive nonmetals
- Period
- 2
- Group
- 16
- Block
- p-block
- Phase at STP
- gas
Electron structure
- Electron configuration
- 1s2 2s2 2p4
- Shorthand configuration
- [He] 2s2 2p4
- Electrons per shell
- 2, 6
- Oxidation states
- -2, -1, +1, +2
Physical properties
- Melting point
- 54.36 K
- Boiling point
- 90.2 K
- Density
- 0.001429 g/cm3
- Phase
- gas
Atomic properties
- Electronegativity (Pauling)
- 3.44
- Atomic radius
- 48 pm
- Covalent radius
- 66 pm
- Van der Waals radius
- 152 pm
- First ionization energy
- 1314 kJ/mol
- Electron affinity
- 141 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| O-16 | 15.99491 | 99.76% | Stable |
Common uses
- Respiration
- Steel manufacturing
- Medical therapy
- Water treatment
Discovery
- Year
- 1774
- Discovered by
- Joseph Priestley, Carl Wilhelm Scheele
- Country
- England/Sweden