Sodium oxide

Sodium oxide
Sodium oxide
CAS number 1313-59-3 YesY
PubChem 73971
UN number 1825
Molecular formula Na2O
Molar mass 61.9789 g/mol
Appearance White solid
Density 2.27 g/cm3
Melting point


Boiling point

1950 °C decomposes

Solubility in water reacts violently to form NaOH
Crystal structure Antifluorite (face centered cubic), cF12
Space group Fm3m, No. 225
Tetrahedral (Na+); cubic (O2–)
Std enthalpy of
−414.2 kJ/mol
Standard molar
75.1 J mol−1 K−1
EU Index Not listed
Main hazards Corrosive, reacts violently with water
Flash point Non-flammable
Related compounds
Other anions Sodium sulfide
Sodium selenide
Sodium telluride
Other cations Lithium oxide
Potassium oxide
Rubidium oxide
Caesium oxide
Related sodium oxides Sodium peroxide
Sodium superoxide
Related compounds Sodium hydroxide
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium oxide (SOX) is a chemical compound with the formula Na2O. It is used in ceramics and glasses, though not in a raw form. Treatment with water affords sodium hydroxide.

Na2O + H2O → 2 NaOH

The alkali metal oxides M2O (M = Li, Na, K, Rb) crystallise in the antifluorite structure. In this motif the positions of the anions and cations are reversed relative to their positions in CaF2, with sodium ions tetrahedrally coordinated to 4 oxide ions and oxide cubically coordinated to 8 sodium ions.[1][2]



Sodium oxide is produced by the reaction of sodium with sodium hydroxide, sodium peroxide, or sodium nitrite:[3]

2 NaOH + 2 Na → 2 Na2O + H2
Na2O2 + 2 Na → 2 Na2O
2 NaNO2 + 6 Na → 4 Na2O + N2

Most of these reactions rely on the reduction of something by sodium, whether it is hydroxide, peroxide, or nitrite.

Burning sodium in air will produce Na2O and about 20% sodium peroxide Na2O2.

6 Na + 2 O2 → 2 Na2O + Na2O2


Glass making

Sodium oxide is a significant component of glasses and windows although it is added in the form of "soda" (sodium carbonate). Sodium oxide does not explicitly exist in glasses, since glasses are complex cross-linked polymers. Typically, manufactured glass contains around 15% sodium oxide, 70% silica (silicon dioxide) and 9% lime (calcium oxide). The sodium carbonate "soda" serves as a flux to lower the temperature at which the silica melts. Soda glass has a much lower melting temperature than pure silica, and has slightly higher elasticity. These changes arise because the silicon dioxide and soda react to form sodium silicates of the general formula Na2[SiO2]x[SiO3].

Na2CO3 → Na2O + CO2
Na2O + SiO2 → Na2SiO3


  1. ^ Zintl, E.; Harder, A.; Dauth B. (1934), "Gitterstruktur der oxyde, sulfide, selenide und telluride des lithiums, natriums und kaliums", Z. Elektrochem. Angew. Phys. Chem. 40: 588–93 
  2. ^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
  3. ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.

External links

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