Copper is one of the earliest metals used by human beings. As early as prehistoric times, people began to mine open-pit copper mines and use the obtained copper to make weapons, tools and other utensils. The use of copper had a far-reaching impact on the progress of early human civilization. Copper is a metal that exists in the earth's crust and ocean. The copper content in the crust is about 0.0 1%, and in some copper deposits, the copper content can reach 3% ~ 5%. Most of the copper in nature exists in the form of compounds, that is, copper ores.

Copper is a transition element with chemical symbol Cu and atomic number 29. Pure copper is a kind of soft metal. When it is just cut, its surface is reddish-orange with metallic luster, and its simple substance is purplish red. Good ductility, high thermal conductivity and electrical conductivity, so it is the most commonly used material in cables, electrical and electronic components, and can also be used as building materials to form a variety of alloys. Copper alloys have excellent mechanical properties and low resistivity, among which bronze and brass are the most important. In addition, copper is also a durable metal, which can be recycled many times without damaging its mechanical properties.

Cu2+ salt is the most common copper compound, and its hydrated ions are often blue, while chlorine as ligand is green. It is the source of the color of chalcocite and turquoise, and has been widely used as a pigment in history. Copper buildings will produce verdigris (basic copper carbonate) after corrosion. Decorative arts mainly use metallic copper and pigments containing copper.

The activity of copper is weak, and the reaction between iron and copper sulfate can replace copper. Copper is insoluble in non-oxidizing acids.

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Copper is a non-ferrous metal closely related to human beings. Widely used in electric power, light industry, machinery manufacturing, construction industry, national defense industry and other fields, second only to aluminum in the consumption of non-ferrous metal materials in China. Copper is a red metal and a green metal. It is said to be a green metal mainly because it has a low melting point and is easy to be remelted and smelted, so it is quite cheap to recycle. In ancient times, it was mainly used for casting utensils, artworks and weapons. Famous vessels and works of art such as stepmother Wu Ding and Siyang Fangzun.

Refer to Baidu Encyclopedia-Copper