Sodium superoxide

Sodium superoxide
IUPAC name
sodium(I) superoxide
Other names
sodium superoxide
12034-12-7 YesY
3D model (Jmol) Interactive image
PubChem 61542
RTECS number WE2860010
Molar mass 54.9886 g/mol
Appearance Yellow to orange crystalline solid
Density 2.2 g/cm3
Melting point 551.7 °C (1,025.1 °F; 824.9 K)
Boiling point Decomposes
Basicity (pKb) N/A
72.1 J/mol K
115.9 J/mol K
-260.2 kJ/mol
-218.4 kJ/mol
R-phrases R35
S-phrases S1/2, S26, S37/39, S45
NFPA 704
Flash point Non flammable
Related compounds
Other anions
sodium oxide
sodium peroxide
Other cations
potassium superoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Sodium superoxide is the inorganic compound with the formula NaO2.[1] This yellow-orange solid is a salt of the superoxide anion. It is an intermediate in the oxidation of sodium by oxygen.


NaO2 is prepared by treating sodium peroxide with oxygen at high pressures:[2]

Na2O2 + O2 → 2 NaO2

It can also be prepared by careful oxygenation of a solution of sodium in ammonia:

Na(in NH3) + O2 → NaO2


The product is paramagnetic, as expected for a salt of the O
anion. It hydrolyses readily to give a mixture of sodium hydroxide, oxygen and hydrogen peroxide.[3] It crystallizes in the NaCl motif.


  1. Hayyan M., Hashim M.A., AlNashef I.M., Superoxide Ion: Generation and Chemical Implications, Chem. Rev., 2016, 116 (5), pp 3029–3085. DOI: 10.1021/acs.chemrev.5b00407
  2. Stephen E. Stephanou, Edgar J. Seyb Jr., Jacob Kleinberg "Sodium Superoxide" Inorganic Syntheses 1953; Vol. 4, 82-85.
  3. Sasol Encyclopaedia of Science and Technology , G.C. Gerrans, P. Hartmann-Petersen , p.243 "sodium oxides" , google books link
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