Nitrogen Fluorine

Oxygen (O)

From Wikipedia, the free encyclopediaOxygen 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.

Oxygen in the periodic table

Symbol

Atomic number

Group

Period

Block

Element category

Nonmetal

Physical properties

Phase at STP

Gas

Density

1.429 g/cm³

Atomic weight

15.999 u

Melting point

54.36 K
-218.79 °C
-361.822 °F

Boiling point

90.188 K
-182.962 °C
-297.3316 °F

Atomic properties

Electronegativity (Pauling Scale)

3.44

Electron affinity

140.976 kJ/mol

Oxidation states

−2, −1, 0, +1, +2
()

Ionization energies

1	1313.9 kJ/mol
2	3388.3 kJ/mol
3	5300.5 kJ/mol
4	7469.2 kJ/mol
5	10989.5 kJ/mol
6	13326.5 kJ/mol
7	71330 kJ/mol
8	84078 kJ/mol

Electron configuration

Elektronkonfiguration (shorthand)

[He] 2s² 2p⁴

Electron configuration

1s² 2s² 2p⁴

Electrons per shell

2, 6

History

Discovered

1771

Discovered by

Carl Wilhelm Scheele

Named by

Antoine Lavoisier