Tin

Tin is one of the first metals worked by humans, mixed with copper to create bronze: the alloy that defined a whole era of prehistory. Today it is still essential in food packaging, electronics soldering, and as an anti-corrosion coating for steel. It is also one of the few metals that produces an audible sound when bent.

• Atomic Number5050 protons, 50 electrons
• Atomic Mass118.71 u50× heavier than hydrogen
• State at Room TempSolidSolid
• Density7.287 g/cm³
• Melting / Boiling231.9°C / 2601.8°C
• DiscoveredAncient

What is Tin?

Tin is a post-transition metal in Group 14 of the periodic table, sitting below germanium. With 50 protons, tin is a soft, silver-white metal that has the interesting property of "tin cry", a creaking or crackling sound when a bar of it is bent, caused by crystal twinning. At very low temperatures, tin undergoes a phase change and crumbles into grey powder (tin pest). Tin has two main oxidation states: +2 (stannous) and +4 (stannic).

Tin's English name comes from Old English and related Germanic words. The chemical symbol Sn comes from the Latin stannum. Tin has been known since at least 3500 BCE and was one of the seven metals of antiquity known to ancient civilisations. The name of the metal has been connected to the Etruscan god Tinia.

Fact Bronze: the alloy of copper and tin, gave its name to an entire age of human prehistory: the Bronze Age (roughly 3300-1200 BCE). The discovery that mixing tin with copper produced a metal harder and more durable than either alone was one of the most transformative technological discoveries in human history, enabling better tools, weapons and agricultural implements.

Where you find Tin

In space

Tin is produced in stars and found in the Sun.

On Earth

Tin makes up approx. 2 parts per million of the Earth's crust and is concentrated mainly in cassiterite deposits.

• Cassiterite (SnO₂). Tin dioxide is the primary ore, found in alluvial (river) deposits and hard rock lodes. China, Indonesia, Peru and Bolivia are the largest producers.
• Cornwall and Devon. The tin mines of southwest England were mined from at least the Bronze Age. Although mostly closed now, they made Britain a major tin exporter for 3,000 years.

How we use Tin

• Tin cans.. Steel food and drink cans are tin-plated, coated with a thin layer of tin to prevent rust and prevent iron from contaminating the food. The layer is extremely thin: only approx. 0.4 microns.
• Solder.. Tin-silver-copper alloys (lead-free solder) and tin-lead alloys join electrical components on circuit boards. Most modern electronics use tin-based lead-free solder required by RoHS regulations.
• Bronze.. Tin alloyed with copper creates bronze: one of the most important alloys in history, used for tools, weapons, bells, coins and sculptures from around 3500 BCE.
• Pewter.. An alloy of tin with antimony and copper, used for decorative items, tankards and cutlery. Historical pewter also contained lead, which is now eliminated for safety.

Did you know? "Tin" cans are actually almost entirely steel. Only a paper-thin coating of tin, approx. 0.4 micrometres thick, covers the inside and outside to prevent rusting and protect the food from the iron beneath. If you recycled every tin can you have ever used, the total amount of tin would barely fill a teaspoon.

How it was discovered

Tin has been known since prehistoric times. Bronze: the copper-tin alloy, was in use in the Middle East by approx. 3500 BCE. Pure tin was smelted in China by around 1800 BCE. Cornwall in Britain was producing tin for Mediterranean bronze-making by 1500 BCE. The chemical isolation and characterisation of tin as a distinct element was established progressively through the 18th century, with Lavoisier listing it as an element in 1789.

Deeper dive: tin chemistry and applications

Tin plague (or tin pest) is a fascinating physical transition that afflicted polar expeditions in the early 20th century. Below approx. 13°C, the normal "white tin" (beta-tin) gradually converts to "grey tin" (alpha-tin), a powdery, crumbly, non-metallic allotrope. This conversion can spread autocatalytically, grey tin causes adjacent white tin to convert. Tin buttons, hinges and solder in equipment at polar temperatures could fail catastrophically. Some historians have suggested tin plague may have contributed to the failures of early Antarctic expeditions, though this remains debated.

The global tin market is tightly linked to electronics manufacturing, because tin is the dominant component of modern lead-free solder. The transition from lead-tin to lead-free solder required by the EU's RoHS Directive (2006) was a major technological challenge, new solders had to match or exceed the reliability of the old lead-tin formulations while eliminating the toxic lead. Tin-silver-copper (SAC) alloys became the industry standard but have a higher melting point and can form tin whiskers, tiny metallic filaments that can cause short circuits, requiring careful engineering to manage.

Moving to 51 protons on the periodic table brings us to Antimony.