Selenium dioxide

  • Formula: SeO2
  • Hill system formula: O2Se1
  • CAS registry number: [7446-08-4]
  • Formula weight: 110.959
  • Class: oxide
  • Colour: white
  • Appearance: crystalline solid
  • Melting point: 340°C
  • Boiling point: 315°C
  • Density: 3950 kg m-3

The following are some synonyms of selenium dioxide:

  • selenium dioxide
  • selenium(IV) oxide
  • selenium oxide

The oxidation number of selenium in selenium dioxide is 4.


Selenium(IV) dioxide is formed by the combustion of elemental selenium in a mixture of oxygen and nitrogen dioxide. The yield is about 80%. Selenium(IV) dioxide is a white crystalline material that melts at 340°C.

Solid state structure

  • Geometry of selenium:
  • Prototypical structure:
Crystal structure of selenium dioxide.
Crystal structure of selenium dioxide.

Element analysis

The table shows element percentages for SeO2 (selenium dioxide).

Element %
O 28.84
Se 71.16

Isotope pattern for SeO2

The chart below shows the calculated isotope pattern for the formula SeO2 with the most intense ion set to 100%.


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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