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Oxygen (O)

Oxygen is a chemical element of the periodic table with chemical symbol O and atomic number 8 with an atomic weight of 15.999 u and is classed as nonmetal and is part of group 16 (oxygen group). Oxygen is gas at room temperature.

Oxygen in the periodic table

Atomic number8
Group16 (Oxygen group)
Color Colorless
Number of protons8 p+
Number of neutrons8 n0
Number of electrons8 e-
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.

Physical properties

Phase at STPGas
Density1.429 g/cm3
Atomic weight15.999 u

Thermal properties

Melting point54.36 K
-218.79 °C
-361.822 °F
Boiling point90.188 K
-182.962 °C
-297.3316 °F
Heat of vaporization3.4109 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)3.44
Electron affinity140.976 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 for oxygen

Electron configuration
Shorthand configuration
[He] 2s2 2p4
Electron configuration
Full configuration
1s2 2s2 2p4
Electron configuration chart
Electrons per shell2, 6
Valence electrons 6
Valency electrons 2
Bohr model
OxygenElectron shell for Oxygen, created by Injosoft ABO
Figure: Shell diagram of Oxygen (O) atom.
Orbital Diagram

The history of Oxygen

DiscoveryCarl Wilhelm Scheele (1771)
First isolationAntoine Lavoisier (1771)
Named byAntoine Lavoisier
Discovery of oxygen
Oxygen was isolated by Michael Sendivogius before 1604, but it is commonly believed that the element was discovered independently by Carl Wilhelm Scheele, in Uppsala, in 1773 or earlier, and Joseph Priestley in Wiltshire, in 1774. Priority is often given for Priestley because his work was published first. Priestley, however, called oxygen "dephlogisticated air", and did not recognize it as a chemical element. The name oxygen was coined in 1777 by Antoine Lavoisier, who first recognized oxygen as a chemical element and correctly characterized the role it plays in combustion. Lavoisier renamed 'vital air' to oxygène in 1777 from the Greek roots ὀξύς (oxys), because he mistakenly believed that oxygen was a constituent of all acids. Chemists (such as Sir Humphry Davy in 1812) eventually determined that Lavoisier was wrong in this regard, but by then the name was too well established.


List of unique identifiers for Oxygen in various chemical registry databases
CAS Number7782-44-7
ChemSpider ID140526
EC number231-956-9
PubChem CID Number977