A malleable, fairly soft, silvery-white, metallic element
in group IVA of the periodic table;
it occurs mainly as cassiterite (tin
dioxide, TnO2), from which it is obtained by smelting with coal.
Tin exhibits allotropy: white (β)
tin, the normal form, changes below 13.2°C to gray (α) tin, a
powdery metalloid form resembling germanium,
and known as "in pest."
| Cassiterite. Credit: Mineral Information
Tin is unreactive, but dissolves in concentrated acids and alkalis, and
is attacked by halogens. It is used to coat
other metals to prevent corrosion, and
forms part of numerous alloys, such as soft
solder, pewter, type metal, and bronze.
|relative atomic mass
Compounds of tin
Tin forms organotin compounds, used in biocides, and also inorganic compounds:
tin (II) and tin (IV) salts. Tin (IV) oxide (SnO2)
is a white powder (sublimes at 1,800°C) prepared by calcining
cassiterite or burning finely divided tin; it is used in glazes and as an
abrasive. Tin (II) chloride
(SnCl2) is a white crystalline solid, prepared by dissolving
tin in hydrochloric acid and used
as a reducing agent, in tin-plating,
and as a mordant. Melting point 246°C,
boiling point 652°C.