Tin Sn

Discovery

Tin has been known since antiquity. From around 3000 BCE people in West Asia and the Mediterranean alloyed it with copper to make bronze for weapons and tools. Harder than copper and easier to cast, bronze drove technological progress.

Tin ores are scarce, however, and had to be traded over long distances. Tin from Cornwall in southwest Britain is traditionally said to have reached the Mediterranean in ancient times, and tin mining there continued until the late twentieth century.

In the modern era, tinplate, steel sheet coated with tin, made the canning industry possible. In the mid-twentieth century the float glass process was developed, in which molten glass is floated on a bath of molten tin to produce perfectly flat sheets.

Origin of the name

The English word tin is Germanic in origin. The symbol Sn comes from the Latin stannum.

Main uses

• Solder: the largest use of tin. Since the EU restricted lead in electronics, lead-free solders of tin with silver and copper have become standard.
• Tinplate: food cans are made of steel coated with a thin layer of tin to prevent rusting.
• Flat glass: most window glass and smartphone cover glass is made by floating molten glass on molten tin.
• Alloys: tin goes into bronze, pewter and Babbitt bearing metals.
• Compounds: stannous fluoride in toothpaste helps prevent decay, and organotin compounds stabilise PVC. Tributyltin, once used in anti-fouling ship paints, harmed marine life and has been banned by international convention.

Isotopes

Tin has ten stable isotopes, tin-112, -114, -115, -116, -117, -118, -119, -120, -122 and -124, the most of any element. This is because 50 protons is a "magic number" that makes nuclei especially stable. Tin-120 is the most abundant. Tin-119 is used in Mössbauer spectroscopy, and tin-126 is a fission product with a half-life of about 230,000 years.

In everyday life

Tin is extracted mainly from cassiterite (tin oxide), with China, Indonesia and Myanmar among the leading producers. Because its trade can finance armed groups in conflict zones, it is regulated as a "conflict mineral" along with tantalum, tungsten and gold.

Metallic tin and inorganic tin compounds have low toxicity, which is why tin is used for food containers, although some organotin compounds are highly toxic.

Pure tin kept below about 13 °C for long periods slowly converts to brittle grey tin, a change called "tin pest". Many stories blame it for crumbling objects in cold places, though most are unverified anecdotes.