In chemistry, gold is chemical element 79, a transition metal in Group 11. It has an atomic weight of 199.966 a.m.u. Its symbol is Au, from the Latin word for gold, aurum. It is a "noble metal" meaning it has low chemical reactivity.
Gold is very soft. It is malleable, meaning a goldsmith can hammer it into thin metal sheets. It is also ductile, which means it can be pulled into wire. When it is used in money or in jewelry, it is often alloyed with silver or some other metal to make it harder.
Most metals are gray in color. Gold is yellow because of the way its electrons behave. The only other metal in common use that has a non-gray color is copper.
Metallic gold is non-toxic, which is unusual for a heavy metal. Soluble gold compounds, however, are toxic to the liver and kidneys.
Gold is a fairly good electrical conductor, but not as good as copper or silver. Copper and brass electrical connectors, especially those used with computer and audio/video equipment, are often plated with gold for corrosion resistance.
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