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"SnO" redirects here. For other uses, see SnO (disambiguation).
Tin(II) oxide
CAS number 21651-19-4 YesY
PubChem 88989
EC number 244-499-5
RTECS number XQ3700000
Jmol-3D images Image 1
Molecular formula SnO
Molar mass 134.709 g/mol
Appearance black or red powder when anhydrous, white when hydrated
Density 6.45 g/cm3
Melting point

1080 °C[1]

Solubility in water insoluble
Crystal structure tetragonal
Std enthalpy of
−285 kJ·mol−1[2]
Standard molar
56 J·mol−1·K−1[2]
EU Index Not listed
Flash point Non-flammable
Related compounds
Other anions Tin sulfide
Tin selenide
Tin telluride
Other cations Carbon monoxide
Silicon monoxide
Germanium(II) oxide
Lead(II) oxide
Related tin oxides Tin dioxide
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Tin(II) oxide (stannous oxide) is a compound with the formula SnO. It is composed of tin and oxygen where tin has the oxidation state of +2. There are two forms, a stable blue-black form and a metastable red form.

Preparation and reactions

Blue-black SnO can be prepared by heating the tin(II) oxide hydrate, SnO.xH2O (x<1) precipitated when a tin(II) salt is reacted with an alkali hydroxide such as NaOH.[3] Metastable, red SnO can be prepared by gentle heating of the precipitate produced by the action of aqueous ammonia on a tin(II) salt.[3] SnO may be prepared as a pure substance in the laboratory, by controlled heating of tin(II) oxalate (stannous oxalate) in the absence of air.[4]

SnC2O4 → SnO + CO2 + CO

Tin(II) oxide burns in air with a dim green flame to form SnO2.[3]

2 SnO + O2 → 2 SnO2

When heated in an inert atmosphere initially disproportionation occurs giving Sn metal and Sn3O4 which further reacts to give SnO2 and Sn metal.[3]

4SnO → Sn3O4 + Sn
Sn3O4 → 2SnO2 + Sn

SnO is amphoteric, dissolving in strong acid to give tin(II) salts and in strong base to give stannites containing Sn(OH)3.[3] It also dissolves in strong acid solutions to give the ionic complexes Sn(OH2)32+ and Sn(OH)(OH2)2+, and in less acid solutions to give Sn3(OH)42+.[3] Note that anhydrous stannites, e.g. K2Sn2O3, K2SnO2 are also known.[5][6][7] SnO is a reducing agent and this appears to its role in the manufacture of so-called "copper ruby glass".[8]


Black, α-SnO adopts the tetragonal PbO layer structure containing four coordinate square pyramidal tin atoms.[9] This form is found in nature as the rare mineral romarchite.[10] The asymmetry is usually simply ascribed to a sterically active lone pair; however, electron density calculations show that the asymmetry is caused by an antibonding interaction of the Sn(5s) and the O(2p) orbitals.[11]
Non-stoichiometry has been observed in SnO.[12]

The electronic band gap has been measured between 2.5eV and 3eV.[13]


The dominant use of stannous oxide is as a precursor in manufacturing of other, typically trivalent, tin compounds or salts. Stannous oxide may also be employed as a reducing agent and in the creation of Red Glass Coloration - A Colorimetric and Structural Study. . It has a minor use as an esterification catalyst.

Cerium(III) oxide in ceramic form, together with Tin(II) oxide (SnO) is used for illumination with UV light.[14]


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