gold

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gold (symbol Au) Naturally occurring metallic element. It is also obtained as a by-product in the refining of copper. It is used in jewellery, connectors for electronic equipment, and as a form of money. Gold in the form of a colloid is sometimes used in colouring glass. The isotope A198 (half-life 2.7 days) is used in radiotherapy. The metal is unreactive but dissolves in aqua regia, a mixture of nitric and hydrochloric acids. Properties: at.no. 79; r.a.m. 196.9665; r.d. 19.30; m.p. 1063°C (1945°F); b.p. 2800°C (5072°F); most common isotope Au197 (100%).

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