Tin
. Tin, symbol Sn, metallic element that has been used by people since ancient times. Tin is in group 14 (or IVa) of the periodic table . The atomic number of tin is 50. Tin has been found in the tombs of ancient Egyptians and was exported to Europe in large quantities from Cornwall, England, during the Roman period. The ancient Egyptians considered tin and lead different forms of the same metal. PROPERTIES AND OCCURRENCE Tin is highly ductile and malleable at a temperature of 100° C (212° F). It is attacked by strong acids. Ordinarily a silver-white metal, at temperatures below 13° C (55° F) it often changes into an allotropic (distinctly different) form known as gray tin, which is an amorphous, grayish powder with a specific gravity of 5.75. Because of the mottled appearance of tin objects undergoing this decomposition, the action is commonly referred to as tin disease or tin pest. Ordinary bar tin, when bent, issues a crackling sound called tin cry, caused by the friction of the tin