Tin (Sn)

Stable isotopes of tin available from ISOFLEX

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Tin was known in ancient times and is mentioned in the Old Testament. Early metal workers found it too soft for most purposes, but when mixed with copper, it produced bronze, which was suitable for many handcrafted items, especially tools and weapons. Tin takes its name from the Anglo-Saxon word tin, and the symbol Sn derives from the Latin word stannum, meaning “tin.”

Tin is a silvery-white metal at ordinary temperatures, slowly changing to gray below 13.2 ºC; it is soft, malleable and somewhat ductile. Tin has two allotropic forms: white tin, the beta form, which has a tetragonal structure and a density of 7.28 g/cm³, its color slowly changing from white to gray when cooled below 13.2 º C, converts to gray tin, the alpha form, with a density of 5.75 g/cm³. The presence of small amounts of antimony or bismuth prevents this transformation from white to gray tin.

Tin is insoluble in water; soluble in HCl, H₂SO₄, aqua regia and alkalis; and slightly soluble in dilute nitric acid. At ordinary temperatures, tin is stable in air, actually forming a very thin protective oxide film. In powder form, and especially in the presence of moisture, it oxidizes. When heated with oxygen, it forms tin oxide. Tin reacts with all halogens to form their halides. Tin is attacked by concentrated acids; with dilute acids, the reaction may be slow or very slow. The metal readily reacts with hot concentrated hydrochloric acid and aqua regia, but more slowly with cold dilute hydrochloric acid. The reaction also is slow with hot dilute sulfuric acid, which dissolves the metal, particularly in the presence of an oxidizing agent. The reaction with nitric acid is also generally slow. Hot concentrated acid converts the metal to an insoluble hydrate tin oxide. Reactions are more rapid with moist sulfur dioxide or sulfurous acid, chlorosulfonic or pyrosulfuric acids. Organic acids — such as acetic, oxalic and citric acids — react slowly with the metal, particularly in the presence of air or an oxidizing agent. The metal is stable in dilute solutions of ammonia or sodium carbonate. Tin dissolves in solutions of oxidizing salts such as potassium chlorate or potassium persulfate. The metal does not react with neutral salts in aqueous solutions; however, it reacts slowly with neutral salts in air. The metal does not combine directly with hydrogen, nitrogen or ammonia gas.

Today, tin is used for plating steel to make “tin” cans for preserving food. Also, tin coats other metals to prevent corrosion. An important application of tin is to produce "float glass" (made by floating molten glass on molten tin) for windows. A number of tin alloys have wide industrial applications and include bronze, solder, Babbit metal, White metal, type metal, fusible metal and phosphor bronze. A tin-niobium alloy that is superconducting at low temperatures is used in the construction of super magnets. Tin is also used in wrapping foil and collapsible tubes.

All organic tin compounds are toxic.

Properties of Tin