Caesium compounds: caesium superoxide

caesium symbol icon

The caesium in caesium superoxide formally is in the oxidation state 1.

Crystal structure of caesium superoxide

Caesium superoxide

  • Formula as often written: CsO2
  • Hill system formula: Cs1O2
  • CAS registry number: [12018-61-0]
  • Formula weight: 164.904
  • Class: oxide


  • caesium superoxide
  • caesium(I) superoxide
  • cesium superoxide
  • cesium(I) superoxide

Physical properties

  • Colour: yellow to orange
  • Appearance: crystalline solid
  • Melting point: 600°C; 432°C
  • Boiling point:
  • Density: 3770 kg m-3


Coming soon...

Element analysis

Element percentages for the elements in caesium superoxide
Element %
Cs 80.60
O 19.40


If caesium is burned in air, the result is mainly formation of orange caesium superoxide, CsO2.

Cs(s) + O2(g) → CsO2(s)

Solid state structure

  • Geometry of caesium:
  • Prototypical structure:

Crystal structure of caesium superoxide

Isotope pattern

What follows is the calculated isotope pattern for the CsO2 unit with the most intense ion set to 100%.

Formula: Cs1O2

mass  %
165 100.0 __________________________________________________
166 0.1
167 0.4


The data on these compounds pages are assembled and adapted from the primary literature and several other sources including the following.

  • R.T. Sanderson in Chemical Periodicity, Reinhold, New York, USA, 1960.
  • N.N. Greenwood and A. Earnshaw in Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
  • F.A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann, in Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
  • A.F. Trotman-Dickenson, (ed.) in Comprehensive Inorganic Chemistry, Pergamon, Oxford, UK, 1973.
  • R.W.G. Wyckoff, in Crystal Structures, volume 1, Interscience, John Wiley & Sons, 1963.
  • A.R.West in Basic solid state chemistry Chemistry, John Wiley & Sons, 1999.
  • A.F. Wells in Structural inorganic chemistry, 4th edition, Oxford, UK, 1975.
  • J.D.H. Donnay, (ed.) in Crystal data determinative tables, ACA monograph number 5, American Crystallographic Association, USA, 1963.
  • D.R. Lide, (ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 77th edition, 1996.
  • J.W. Mellor in A comprehensive treatise on inorganic and theoretical chemistry, volumes 1-16, Longmans, London, UK, 1922-1937.
  • J.E. Macintyre (ed.) in Dictionary of inorganic compounds, volumes 1-3, Chapman & Hall, London, UK, 1992.

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caesium atomic number