Oxygen

Atomic number

8

Atomic mass (u)

15.999

Category

Nonmetal

Standard state

Gas

Melting point

-218.79 °C (54.36 K)

Boiling point

-182.95 °C (90.2 K)

Density (g/cm³)

0.001429

Electronegativity (Pauling)

3.44

Electron configuration

[He]2s2 2p4

Oxidation states

-2

Atomic radius (pm)

152

First ionization energy (eV)

13.618

Discovery & recognition

Discovery year / period (PubChem)

1774

Discovery credited to (RSC)

Joseph Priestley in Wiltshire, England and independently by Carl Wilhelm Scheele in Uppsala, Sweden

Date or period recorded by RSC

1774

Discovery place

Not supplied in the structured record; see the RSC history source.

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

The creation of an element’s nuclei and its concentration into terrestrial deposits are different processes. The occurrence note below concerns its presence or production on Earth; it is not a complete account of nucleosynthesis.

“Oxygen makes up 21% of the atmosphere by volume.”

Royal Society of Chemistry · occurrence excerpt ↗

Continue the research

Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.