8
O
Oxygen
15.999
Oxygen (O)
NonmetalGroup 16Period 2p-block-block
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.
Latin name: Oxygenium
Atomic Number
8
Atomic Mass
15.999 g/mol
Phase (STP)
Gas
Electron Config.
[He] 2s² 2p⁴
General
SymbolO
Atomic Number8
Atomic Mass15.999 g/mol
CategoryNonmetal
Group16
Period2
Blockp-block
Electron Configuration[He] 2s² 2p⁴
Valence Electrons6
ColourColorless gas
CAS NumberCAS7782-44-7
Physical Properties
Phase (STP)Gas
Density0.001429 g/cm³
Melting Point-218.79°C · -361.82°F · 54.36 K
Boiling Point-182.95°C · -297.31°F · 90.20 K
Atomic Properties
Atomic Radius48 pm
Covalent Radius66 pm
Van der Waals Radius152 pm
Electronegativity3.44 Pauling
Ionization Energy1314 kJ/mol
Electron Affinity141 kJ/mol
Oxidation States-2, -1, +1, +2
Ion ChargeO²⁻
Electromagnetic
Electrical TypeInsulator
Abundance
In Universe1.0000%
In Sun0.9000%
In Earth's Crust46.0000%
In Oceans86.0000%
In Humans61.0000%
In Meteorites40.0000%
Discovery & History
Discovery Year1774
Discovered ByCarl Wilhelm Scheele
Named ByAntoine Lavoisier
Isotopes of Oxygen
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| O-16 | 99.757% | Stable | — |
| O-17 | 0.038% | Stable | — |
| O-18 | 0.205% | Stable | — |