Copper (Cuprum) is a metal element, is also a transition element, chemical symbol Cu, English copper, atomic number 29. Pure copper is a soft metal with a red-orange metallic luster when cut and a purplish red color in its elemental form. Ductility, high thermal and electrical conductivity, so the cable and electrical, electronic components are the most commonly used materials, can also be used as building materials, can be composed of many kinds of alloys. Copper alloys have excellent mechanical properties and low electrical resistivity, of which the most important are bronze and brass. Copper is also a durable metal that can be recycled many times without damaging its mechanical properties.

Divalent copper salts, the most common copper compound, are often blue in their hydration ions and green in their chlorine ligands. They are the source of colour for minerals such as azurite and turquoise and have historically been widely used as pigments. The corrosion of copper building structures produces verdigris (basic copper carbonate). Decorative art mainly uses copper and copper-containing pigments.

Copper was one of the earliest metals used by man. As early as prehistoric times, people began to mine open-pit copper and use it to make weapons, tools and other utensils. The use of copper had a profound impact on the progress of early human civilization. Copper is a metal found in the earth’s crust and oceans. The copper content in the earth’s crust is about 0.01%, and in individual copper deposits, the copper content can reach 3% ~ 5%. Most of the copper in nature is found in compounds called copper ores.

The activity of copper is weak, and the reaction of iron and copper sulfate can replace copper. Copper is insoluble in nonoxidizing acids.