Silver

Silver is a soft, lustrous metal in group 11 with copper and gold. Its configuration is [Kr] 4d10 5s1: a full d subshell beneath a single, loosely held s electron. That lone electron moves freely through the metal, giving silver the highest electrical and thermal conductivity of any element. The same mobile electrons reflect about 95% of visible light, more than any other metal, which is why silver has backed the best mirrors since the 19th century. Silver almost always forms compounds in the +1 state, and it does not react with oxygen or water at ordinary temperatures.

Silver does react with sulfur. Traces of hydrogen sulfide in air turn it black with silver sulfide, the tarnish that coats old spoons. Silver halides are sensitive to light: a photon can free a silver atom from silver bromide, the basis of film photography for over a century. Today the largest industrial demand is for electrical contacts and the conductive paste printed on silicon solar cells. Silver ions are toxic to bacteria at very low concentrations, so silver is used in wound dressings and water filters. Mexico, China and Peru are the leading producers.

Discovery

Silver has been used since prehistory. By around 3000 BCE, people in Anatolia and Mesopotamia were extracting it from lead ores by cupellation, melting the ore and blowing air over it so that the lead oxidizes and silver remains. Laurion's mines financed Athens' navy, and from 1545 the Cerro Rico of Potosí in Bolivia poured silver into the Spanish empire. The English name comes from Old English seolfor; the symbol Ag is from Latin argentum, which also gave Argentina its name.