Tin(II) oxide (stannous oxide) is a compound with the formula SnO. It is composed of tin and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

where tin has the oxidation state of +2. There are two forms, a stable blue-black form and a

metastable In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball i ...

red form.

Preparation and reactions

Blue-black SnO can be produced 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.Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier
Metastable, red SnO can be prepared by gentle heating of the precipitate produced by the action of aqueous ammonia on a tin(II) salt.
SnO may be prepared as a pure substance in the laboratory, by controlled heating of tin(II) oxalate (

stannous oxalate Tin(II) oxalate is an inorganic compound, a salt of tin and oxalic acid with the chemical formula . The compound looks like colorless crystals, does not dissolve in water, and forms crystalline hydrates. Synthesis Effect of oxalic acid solution on ...

) in the absence of air or under a CO₂ atmosphere. This method is also applied to the production of ferrous oxide and manganous oxide. :SnC₂O₄·2H₂O → SnO + CO₂ + CO + 2 H₂O Tin(II) oxide burns in air with a dim green flame to form SnO₂. :2 SnO + O₂ → 2 SnO₂ When heated in an inert atmosphere initially

disproportionation In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. More generally, the term can ...

occurs giving Sn metal and Sn₃O₄ which further reacts to give SnO₂ and Sn metal. :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⁻. It can be dissolved 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⁺. Note that anhydrous stannites, e.g. K₂Sn₂O₃, K₂SnO₂ are also known. SnO is a reducing agent and is thought to reduce copper(I) to metallic clusters in the manufacture of so-called "copper ruby glass".

Structure

Black, α-SnO adopts the tetragonal PbO layer structure containing four coordinate square pyramidal tin atoms. This form is found in nature as the rare mineral romarchite. 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. The electronic structure and chemistry of the lone pair determines most of the properties of the material. Non-stoichiometry has been observed in SnO. The electronic band gap has been measured between 2.5 eV and 3eV.

Uses

The dominant use of stannous oxide is as a precursor in manufacturing of other, typically divalent, tin compounds or salts. Stannous oxide may also be employed as a reducing agent and in the creation of ruby glass. It has a minor use as an

esterification In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

catalyst. Cerium(III) oxide in

ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, ...

form, together with Tin(II) oxide (SnO) is used for illumination with UV light.

References

{{Oxides Amphoteric compounds Oxides Reducing agents Tin(II) compounds