Discovered | Name | Characteristics | Reactions | Uses | Alloys

Tin is a metal in Group IVA and the 5th period. Other members of the group are carbon (C), silicon (Si), germanium (Ge), and lead (Pb).

The metal has been known for centuries. Therefore, it is not surprising that its name is an Anglo-Saxon word, but the symbol Sn comes from the Latin name for the metal, stannum.

Tin metal exists in two allotropic forms: b (white tin, body-centered tetragonal) and a (gray, diamond cubic). The ordinary form at room temperature is b tin, which is a silver-white malleable metal that is somewhat ductile. When b tin is bent or handled roughly, it literally "cries", making a high pitched sound, due to a change in the crystalline structure.

When heated in air, tin forms SnO2, and the metal is attacked by nitric acid at room temperature and hydrochloric acid when heated

Sn(s) + 2 HCl(aq) SnCl2(aq) + H2(g)

It also reacts with strong base when heated. It does not react with water, but does react with steam. The most important compound is tin(II) chloride (SnCl2·2H2O),

Sn(s) + Cl2(g) SnCl2(s)

which is widely used as a reducing agent.

Tin exists as Sn(II) or Sn(IV) in its compounds.

Tin played a role in the development of civilization, as it is an important constituent of bronze, an alloy of Cu with 5-10% Sn. Bronze was used in Mesopotamia and in Egypt throughout recorded history. In South America, pure tin was found in Machu Picchu, the mountain home of the Incas, who apparently made bronze objects with varying compositions of Cu and Sn depending on the final use of the implement.

The metal was used by the Egyptians, the Phoenicians, the Greeks, and the Romans, and is mentioned in the Bible. Since the mineral cassiterite (SnO2) is the only important tin-containing ore, it must also have been known to the ancients. It was traded by the Phoenicians, and it has been said - although it is apparently a myth - that they found cassiterite in England and gave the name Cassiterides to those islands. Tin dishes have been used for hundreds of years, and tin plated iron was mentioned in 320 B.C. by Theophrastus. Cassiterite was mined in Cornwall, England for centuries, but tin ore now comes largely from Southeast Asia and Bolivia.

If b tin is held at a temperature lower than 13.2°C, it changes to a tin, which is weak and crumbly. This change from b to a tin is called "tin disease" and was the cause of crumbling tin organ pipes in cold churches and cathedrals in past centuries. There is also an old myth that says that Napoleon's troops lost their trousers when their tin buttons crumbled in the cold Russian winter of 1812 and that that contributed to their defeat.

Due to its high cost and low strength, pure tin metal is rarely used. Rather it is used in various alloys and as a tin coating on steel. Indeed, tin plating accounts for 40% of the tin used. Tin is non-toxic and protects the underlying steel from corrosion. Thus, soft drinks and foods are packaged in such cans. At least 30,000 million such cans are sold each year in the U.S. alone!

The following are the main alloys of tin -