Tin oxide (stannous oxide) is a compound 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. 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) in the absence of air.

SnC₂O₄ → SnO + CO₂ + CO

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

Tin dioxide

Tin dioxide is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the main ore of tin. With many other names , this oxide of tin is the most important raw material in tin chemistry...

.

2 SnO + O₂ → 2 SnO₂

When heated in an inert atmosphere initially disproportionation

Disproportionation

Disproportionation, also known as dismutation is used to describe a specific type of redox reaction in which a species is simultaneously reduced and oxidized so as to form two different products....

 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 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⁺. Note that anhydrous stannites, e.g. K₂Sn₂O₃, K₂SnO₂ are also known.
SnO is a reducing agent and this appears to its role in the manufacture of so-called "copper ruby glass".

Structure

Black, α-SnO adopts the tetragonal PbO

Lead(II) oxide

Lead oxide is the inorganic compound with the formula PbO. Lead oxide occurs in two polymorphs, red, having a tetragonal crystal structure and yellow, having an orthorhombic crystal structure...

 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.

Non-stoichiometry has been observed in SnO.

The electronic band gap has been measured between 2.5eV

Electronvolt

In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...

 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

Cranberry glass

Cranberry glass is a red glass made by adding gold chloride to molten glass. Tin, in the form of stannous chloride, is sometimes added in tiny amounts as a reducing agent...

. It has a minor use as an esterification catalyst.

Cerium(III) oxide

Cerium(III) oxide

Cerium oxide is an oxide of the rare earth metal cerium. It has chemical formula Ce2O3, and is gold-yellow in color.-Exhaust catalysts:...

 in ceramic

Ceramic

A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

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