Tin is a chemical element with the symbol Sn and atomic number 50. It is a silvery metal that characteristically has a faint yellow hue. It like indium, is soft enough to be cut without much force. Pure Sn after solidifying keeps a mirror-like appearance similar to most metals. However, in most tin alloys (such as pewter), the metal solidifies with a dull gray color. It 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. It 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. It is the 49th most abundant element on Earth and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table, thanks 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, but at low temperatures, it transforms into the less dense grey α-tin, which has the diamond cubic structure. Metallic Sn does not easily oxidize in air.
Physical Characteristics of Tin
- It 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.
- It melts at low temperatures of about 232 °C (450 °F), the lowest in group 14. The melting point is further lowered to 177.3 °C (351.1 °F) for 11 nm particles.
- It resists corrosion from water, but can be attacked by acids and alkalis. Tin can be highly polished and is used as a protective coat for other metals. A protective oxide (passivation) layer prevents further oxidation, the same that forms on pewter and other tin alloys.