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Metallic chemical element , one of the transition element s, chemical symbol Cu, atomic number 29.
Sometimes found in the free state in nature, it is a reddish metal , very ductile and an unusually good conductor of electricity and heat. Most of the world's copper production is used by the electrical industries; the remainder is combined with other metals (e.g., zinc, tin, nickel) to form alloy s such as brass , bronze , nickel silver, and Monel. Copper is part of nearly all coinage metals. In compounds copper usually has valence 1 (cuprous) or 2 (cupric). Cuprous compounds include cuprous oxide, a red pigment and a fungicide; cuprous chloride, a catalyst for certain organic reactions; and cuprous sulfide, with a variety of uses. Cupric compounds include cupric oxide, a pigment, decolorizing agent, and catalyst; cupric chloride, a catalyst, wood preservative, mordant, disinfectant, feed additive, and pigment; and cupric sulfate, a pesticide, germicide, feed additive, and soil additive. Copper is a necessary trace element in the human diet and essential to plant growth; in blue-blooded mollusks and crustaceans it plays the same role in hemocyanin as iron does in hemoglobin .
Crystalline copper from Michigan
By courtesy of Ted Boente Collection; photograph, John H. Gerard
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[c mediumvioletred] (as used in expressions)
Copper Age
{{link=porphyry copper deposit">porphyry copper deposit