Tin is the chemical element with symbol Sn and atomic number 50. It is a soft, silvery metal in group 14 with a low melting point, good corrosion resistance and a long technological history in bronze, solder and protective coatings.
Tin quick facts
| Property | Value |
| Symbol | Sn |
| Atomic number | 50 |
| Relative atomic mass | 118.710 |
| Group | 14 |
| Period | 5 |
| Block | p-block |
| Density | 7.287 g/cm³ |
| Melting point | 231.928°C |
| Boiling point | 2586°C |
| Electron configuration | [Kr] 4d¹⁰ 5s² 5p² |
| Common oxidation states | +2, +4 |
| CAS number | 7440-31-5 |
| Key natural isotope | ¹²⁰Sn |
Position and chemistry
Tin is in group 14, period 5 and the p-block. Its electron configuration is [Kr] 4d¹⁰ 5s² 5p². Tin commonly forms compounds in the +2 and +4 oxidation states.
See the complete CleverlySmart periodic table.
Allotropes: white tin and grey tin
At ordinary temperatures, the stable metallic form is white tin (β-tin). Below about 13.2°C, tin can slowly transform into grey tin (α-tin), a nonmetallic, brittle form with a diamond-like crystal structure. This transformation is sometimes called tin pest because affected objects can become crumbly.
Impurities and alloying elements can strongly influence the transformation rate, so real-world tin objects do not necessarily disintegrate simply because they are cold.
Important tin compounds
- Tin(II) chloride (SnCl₂): a reducing agent and industrial chemical used in plating, dyeing and synthesis.
- Tin(IV) oxide (SnO₂): used in ceramics, gas sensors, transparent conductive coatings and polishing materials.
- Organotin compounds: used in specialised catalysts and polymer chemistry; some older antifouling compounds such as tributyltin caused severe environmental harm and have been heavily restricted.
- Stannates: tin-containing oxides used in ceramics and flame-retardant systems.
Occurrence and production
The most important tin ore is cassiterite (SnO₂). Ore is concentrated and reduced at high temperature to produce metallic tin. Because tin deposits can occur in alluvial sediments as well as hard rock, mining methods vary widely.
Uses of tin
- Tinplate: steel coated with tin resists corrosion and is widely used in food cans and containers.
- Solder: tin is the principal component of many lead-free electronic solders.
- Bronze: copper-tin alloys have been important for tools, bearings, bells, sculpture and marine hardware for thousands of years.
- Float glass: molten glass is floated on molten tin to create extremely flat window glass.
- Superconductors: Nb₃Sn is a high-field superconducting material used in advanced magnets.
Tin isotopes
Tin has ten stable naturally occurring isotopes, more than any other element. They range from tin-112 to tin-124, with ¹²⁰Sn among the most abundant. This unusually large number reflects particularly stable nuclear configurations near atomic number 50.
For broader isotope information, see the CleverlySmart isotope table.
Biological role and safety
Tin has no established essential biological role in humans. Metallic tin and many inorganic tin compounds have relatively low toxicity compared with heavy metals such as cadmium, but organotin compounds can be significantly more toxic and environmentally persistent.
History and name
Tin has been used since prehistoric times, especially as the alloying element that turns copper into bronze. The symbol Sn comes from the Latin stannum.
Frequently asked questions
Are tin cans made entirely of tin?
No. Most “tin cans” are steel coated with a thin protective layer of tin.
What is tin pest?
It is the slow low-temperature transformation of metallic white tin into brittle grey tin.
Deeper look at tin: allotropes and phase changes
Tin is unusual because it has several allotropes. At ordinary temperatures the stable metallic form is beta-tin, a silvery metal with a tetragonal crystal structure, a density of about 7.31 g/cm³, a melting point near 231.9 °C and a boiling point near 2,602 °C. Below about 13.2 °C, another form called alpha-tin becomes thermodynamically favoured. Alpha-tin has a diamond-like structure and is brittle and non-metallic.
The slow transformation from beta-tin to alpha-tin is known as tin pest. It can cause metallic tin to crumble under prolonged cold conditions, although impurities and temperature history strongly affect how quickly the change occurs.
Why tin is so useful in alloys and coatings
Tin resists corrosion and bonds readily with many metals. A thin tin coating protects steel food cans from rust, while tin-based solders create reliable electrical and mechanical joints at relatively low temperatures. Modern lead-free solders commonly combine tin with silver, copper or other elements.
Tin also has a long metallurgical history. Bronze, primarily copper alloyed with tin, was one of the materials that transformed tools, weapons and art in ancient societies.
Important tin compounds
- Tin(II) chloride (SnCl₂): used as a reducing agent and in chemical processing.
- Tin(IV) oxide (SnO₂): used in ceramics, sensors, transparent conducting materials and polishing applications.
- Organotin compounds: useful in some industrial chemistry, but several are tightly restricted because certain organotin species are highly toxic to aquatic life.
Tin isotopes and nuclear science
Tin has more stable isotopes than any other element. This unusually rich isotope pattern makes tin important in nuclear-structure research and produces a complex natural isotopic composition.
Frequently asked questions
What is tin pest?
Tin pest is the gradual conversion of metallic beta-tin into brittle alpha-tin at low temperatures. The change expands the material and can make it break apart.
Why is tin used in food cans?
A very thin tin coating helps protect the underlying steel from corrosion while remaining suitable for food-packaging applications when manufactured to applicable standards.
