- Tin (Sn) is a post-transition metal with atomic number 50, located in Group 14 of the periodic table alongside carbon, silicon, germanium, and lead.
- It is a soft, malleable, silvery-white metal known for its resistance to corrosion and its ability to form useful alloys.
- Tin has four valence electrons—two in the 5s subshell and two in the 5p subshell—and it commonly exhibits oxidation states of +2 and +4, with +4 being more stable in most compounds. Its atomic structure consists of fifty protons, typically sixty-nine neutrons, and fifty electrons arranged in five shells.
- Naturally occurring tin consists of ten stable isotopes, the most abundant being tin-120 (¹²⁰Sn), which makes up 32.6% of natural tin, making it one of the elements with the greatest number of stable isotopes.
- Tin has been known since antiquity and was a vital component of bronze, an alloy of copper and tin that marked the Bronze Age around 3000 BCE. Its resistance to corrosion, especially from water, made it valuable for coating other metals. The primary source of tin is the mineral cassiterite (SnO₂), which is found in alluvial deposits and hard rock mines. Major tin-producing countries include China, Indonesia, Myanmar, Peru, and Bolivia.
- Tin was recognized as a distinct metal in ancient times and has been mined for over 5,000 years. Historical tin trade routes connected regions such as Cornwall in England, the Malay Archipelago, and the Mediterranean civilizations. The name “tin” is of Anglo-Saxon origin, while its chemical symbol Sn comes from the Latin stannum.
- In modern applications, tin is used primarily for plating steel to make tinplate, which is widely used in food packaging to prevent corrosion. It is also a key component of many alloys, such as bronze (copper and tin), pewter (tin, antimony, and copper), and various solders. The shift to lead-free solders in electronics has increased tin demand, as tin is now the primary metal used in these solder alloys.
- Chemically, tin is relatively unreactive. In the +4 oxidation state, it forms compounds such as tin(IV) oxide (SnO₂), an important catalyst and polishing agent, and tin(IV) chloride (SnCl₄), used in chemical synthesis. In the +2 oxidation state, compounds like tin(II) chloride (SnCl₂) are used as reducing agents and in electroplating. Tin also exhibits allotropy: at temperatures above 13.2 °C, it exists as metallic white tin (β-tin), but below this temperature, it can slowly transform into brittle gray tin (α-tin), a phenomenon known as “tin pest.”
- Biologically, tin has no essential role in humans, and most tin compounds have low toxicity. However, certain organotin compounds, such as tributyltin (TBT), are highly toxic and have been widely used as biocides in marine antifouling paints, leading to significant environmental damage before being banned or restricted in many countries.
- From an environmental perspective, tin mining can lead to deforestation, soil erosion, and water pollution, particularly from artisanal mining in tropical regions. Recycling of tin from scrap metal, electronics, and solder waste is an increasingly important source of supply, helping reduce the need for new mining and mitigating environmental impacts.
