Metallic chemical element, chemical symbol Sn, atomic number 50. It is a soft, silvery white metal with a bluish tinge, employed since antiquity in the traditional form of bronze, its alloy with copper. It occurs chiefly as the dioxide (stannic oxide, SnO) in cassiterite. Since it is nontoxic, ductile, malleable, and easily worked, it is used to plate steel cans (tin cans) for use as food containers and to coat and plate other items. Pure tin is too weak to be used alone, but its many alloys include soft solder, pewter, bronze, and low-temperature casting alloys. It has valence 2 or 4 in compounds, including stannous chloride (used in tin galvanizing and manufacturing polymers and dyes), stannous oxide (used to make tin salts for chemical reagents and plating), stannous fluoride (used as an anticavity ingredient in toothpastes), stannic chloride (a stabilizer for perfumes and a source of other tin salts), and stannic oxide (a catalyst and a polishing powder for steel). Tin bonds with carbon to form organotin compounds, used to stabilize PVC and in biocides and fungicides.