Post-transition metal
Tin is a chemical element; it has the symbol Sn (from Latin stannum) and atomic number 50. A metallic-gray metal, tin is soft enough to be cut with little force, and a bar of tin can be bent by hand with little effort. When bent, a bar of tin makes a sound, the so-called "tin cry", as a result of twinning in tin crystals.
Tin is a post-transition metal in group 14 of the periodic table of elements. It is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO2. Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, and has two main oxidation states, +2 and the slightly more stable +4. Tin is the 49th most abundant element on Earth, making up 0.00022% of its crust, and with 10 stable isotopes, it has the largest number of stable isotopes in the periodic table, due to its magic number of protons.
It has two main allotropes: at room temperature, the stable allotrope is β-tin, a silvery-white, malleable metal; at low temperatures it is less dense grey α-tin, which has the diamond cubic structure. Metallic tin does not easily oxidize in air or water.
The first tin alloy used on a large scale was bronze, made of 1⁄8 tin and 7⁄8 copper (12.5% and 87.5% respectively), from as early as 3000 BC. After 600 BC, pure metallic tin was produced. …
Tin extraction and use can be dated to the beginnings of the Bronze Age around 3000 BC, when it was observed that copper objects formed of polymetallic ores with different metal contents had different physical properties. The earliest bronze objects had a tin or arsenic content of less than 2% and are believed to be the result of unintentional alloying due to trace metal content in the copper ore. The addition of a second metal to copper increases its hardness, lowers the melting temperature, and improves the casting process by producing a more fluid melt that cools to a denser, less spongy metal. This was an important innovation that allowed for the much more complex shapes cast in closed molds of the Bronze Age. Arsenical bronze objects appear first in the Near East where arsenic is commonly found with copper ore, but the health risks were quickly realized and the quest for sources of the much less hazardous tin ores began early in the Bronze Age. This created the demand for rare tin metal and formed a trade network that linked the distant sources of tin to the markets of Bronze Age cultures.
Cassiterite (SnO2), the oxide form of tin, was most likely the original source of tin. Other tin ores are less common sulfides such as stannite that require a more involved smelting process. Cassiterite often accumulates in alluvial channels as placer deposits because it is harder, heavier, and more chemically resistant than the accompanying granite. …
Tin is a soft, malleable, ductile and highly crystalline silvery-white metal. When a bar of tin is bent a crackling sound known as the "tin cry" can be heard from the twinning of the crystals. This trait is shared by indium, cadmium, zinc, and mercury in its solid state. Tin melts at about 232 °C (450 °F), the lowest in group 14, and boils at 2,602 °C (4,716 °F), the second lowest (ahead of lead) in its group. The melting point is further lowered to 177.3 °C (351.1 °F) for 11 nm particles.
β-tin, also called white tin, is the allotrope (structural form) of elemental tin that is stable at and above room temperature. It is metallic and malleable, and has body-centered tetragonal crystal structure. α-tin, or gray tin, is the nonmetallic form. It is stable below 13.2 °C (55.8 °F) and is brittle. α-tin has a diamond cubic crystal structure, as do diamond and silicon. α-tin does not have metallic properties because its atoms form a covalent structure in which electrons cannot move freely. α-tin is a dull-gray powdery material with no common uses other than specialized semiconductor applications. γ-tin and σ-tin exist at temperatures above 161 °C (322 °F) and pressures above several GPa.
In cold conditions β-tin tends to transform spontaneously into α-tin, a phenomenon known as "tin pest" or "tin disease". …
Tin is generated via the long s-process in low-to-medium mass stars (with masses of 0.6 to 10 times that of the Sun), and finally by beta decay of the heavy isotopes of indium.
Tin is the 49th most abundant element in Earth's crust, representing 2 ppm compared with 75 ppm for zinc, 50 ppm for copper, and 14 ppm for lead.
Tin does not occur as the native element but must be extracted from various ores. Cassiterite (SnO2) is the only commercially important source of tin, although small quantities of tin are recovered from complex sulfides such as stannite, cylindrite, franckeite, canfieldite, and teallite. Minerals with tin are almost always associated with granite rock, usually at a level of 1% tin oxide content.
Because of the higher specific gravity of tin dioxide, about 80% of mined tin is from secondary deposits found downstream from the primary lodes. Tin is often recovered from granules washed downstream in the past and deposited in valleys or the sea. The most economical ways of mining tin are by dredging, hydraulicking, or open pits. Most of the world's tin is produced from placer deposits, which can contain as little as 0.015% tin.
About 253,000 tonnes of tin were mined in 2011, mostly in China (110,000 t), Indonesia (51,000 t), Peru (34,600 t), Bolivia (20,700 t) and Brazil (12,000 t). Estimates of tin production have historically varied with the market and mining technology. …
In 2018, just under half of all tin produced was used in solder. The rest was divided between tin plating, tin chemicals, brass and bronze alloys, and niche uses.
Pigment Yellow 38, tin(IV) sulfide, is known as mosaic gold.
Purple of Cassius, Pigment Red 109, a hydrous double stannate of gold, was mainly, in terms of painting, restricted to miniatures due to its high cost. It was widely used to make cranberry glass. It has also been used in the arts to stain porcelain.
Lead-tin yellow (which occurs in two yellow forms — a stannate and a silicate) was a pigment that was historically highly important for oil painting and which had some use in fresco in its silicate form. Lead stannate is also known in orange form but has not seen wide use in the fine arts. It is available for purchase in pigment form from specialist artists' suppliers. There is another minor form, in terms of artistic usage and availability, of lead-tin yellow known as Lead-tin Antimony Yellow also known as Naples Yellow.
Cerulean blue, a somewhat dull cyan chemically known as cobalt stannate, continues to be an important artists' pigment. Its hue is similar to that of Manganese blue, Pigment Blue 33, although it lacks that pigment's colorfulness and is more opaque. Artists typically must choose between cobalt stannate and manganese blue imitations made with phthalocyanine blue green shade (Pigment Blue 15:3), as industrial production of manganese blue pigment ceased in the 1970s. …
Tin has seven to ten stable isotopes, the greatest number of any element. Their mass numbers are 112, 114, 115, 116, 117, 118, 119, 120, 122, and 124. Seven, 114-120Sn, are theoretically stable, while the remaining three, 112Sn, 122Sn, and 124Sn, are potentially radioactive to double beta decay, but have not been observed to decay. Tin-120 makes up almost a third of all tin. Tin-118 and tin-116 are also common. Tin-115 is the least common stable isotope. The isotopes with even mass numbers have no nuclear spin, while those with odd mass numbers have a nuclear spin of 1/2. It is thought that tin has such a great multitude of stable isotopes because of tin's atomic number being 50, which is a "magic number" in nuclear physics.
Tin is one of the easiest elements to detect and analyze by NMR spectroscopy, which relies on molecular weight and its chemical shifts are referenced against tetramethyltin (SnMe4).
Of the stable isotopes, tin-115 has a high neutron capture cross section for thermal neutrons, at 30 barns. Tin-117 has a cross section of 2.3 barns, one order of magnitude smaller, while tin-119 has a slightly smaller cross section of 2.2 barns. Before these cross sections were well known, it was proposed to use tin-lead solder as a coolant for fast reactors because of its low melting point. Current studies are for lead or lead-bismuth reactor coolants because both heavy metals are nearly transparent to fast neutrons, with very low capture cross sections. …
Cases of poisoning from tin metal, its oxides, and its salts are almost unknown. On the other hand, certain organotin compounds are almost as toxic as cyanide.
Exposure to tin in the workplace can occur by inhalation, skin contact, and eye contact. The US Occupational Safety and Health Administration (OSHA) set the permissible exposure limit for tin exposure in the workplace as 2 mg/m3 over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) determined a recommended exposure limit (REL) of 2 mg/m3 over an 8-hour workday. At levels of 100 mg/m3, tin is immediately dangerous to life and health.