Copper is a transition element, chemical symbol Cu, English copper, atomic number 29. Pure copper is a soft metal. The surface is freshly cut red and orange with metallic luster. Ductility, thermal conductivity and conductivity are high, so the most commonly used materials, such as cables and electrical components, are also used as building materials, which can form many kinds of alloys. Copper alloys have excellent mechanical properties and low resistivity, the most important of which are bronze and brass. In addition, copper is also a durable metal that can be recycled without compromising its mechanical properties.
Bivalent copper salt is the most common copper compounds, the hydrated ion is blue, and chloride ligand is green, is the source of azurite and turquoise minerals such as color, was widely used as a pigment in history. Copper green (alkali carbonate) is produced when the copper structure is corroded. Decorative arts mainly use copper and copper pigments.
Copper is one of the earliest metals used by man. As early as prehistoric times, people began to excavate open copper mines and use the copper to make weapons, tools and other utensils, and the use of copper had a profound effect on the progress of early human civilization. Copper is a metal found in the earth's crust and oceans. Copper has a content of about 0.01% in the crust, and copper in individual copper deposits can reach 3% to 5%. Copper, in nature, is mostly found in compounds called copper ores.
Copper has a weak activity, and copper and copper sulfate can be replaced by copper. Copper is not soluble in non - oxidized acid.
Various fields of use
Copper is related very closely to human and non-ferrous metals, have been widely used in electrical, light industry, machinery manufacturing, construction industry, defense industry and other fields, in China the consumption of non-ferrous metal materials after aluminum. Copper is a kind of red metal and is also a kind of green metal. It is green metal, mainly because it has a low melting point and easy to melt and smelt again, so recycling is quite cheap. The ancient times were mainly used for the casting of utensils, art and weapons, and the more famous vessels and works of art such as the smother and the four sheep.
Electronics and electronics
Electrical and electronic markets make up about 28% of the total. In 1997, the two markets became the second largest end user of copper consumption, with a 25% market share. In many electric products, (such as transformer winding wire, bus, and heavy motor, telephone line and telephone cable) the service life of copper is fairly long, only after 20 to 50 years later, the inside of the copper can be recycling. Other copper and electronic products (such as small electronics and consumer electronics) have a shorter lifespan, typically 5-10 years. Commercial electronics and large electrical appliances are usually recycled because they contain precious metals other than copper. Still, the recycling rate for small electronic consumer products is fairly low, because there is little copper in them.
With the rapid development of science and technology in the field of electronics, some obsolete copper products are becoming obsolete. In the 80 s, for example, telephone switching station, and the central place of business is the main source of copper and copper alloy scrap, but digital conversion, the advent of the metal intensive things become more and more out of date.
Transport is the third-largest market for copper, about 13 per cent of the total, roughly the same as in the 1960s. Although the importance of transportation has not changed, the use of copper has changed greatly. For many years, automatic radiators were the most important end users in this area; However, the use of copper in automatic electronics and electronics has grown rapidly, while the use of the heat exchanger market has declined. The average life of a car is 10-15 years, and almost all of the copper (including radiators and wiring) is recovered and recycled in its entirety
Industrial machinery and equipment
Industrial machinery and equipment are another major application market, in which copper tends to have long service life. COINS and arms are the main end users in this area. Bullets are rarely recovered, some COINS can be melted, and many are kept by collectors or savers and cannot be recycled.  is used to manufacture industrial valves and accessories, gauges, sliding bearings, molds, heat exchangers and pumps in mechanical and transport vehicle manufacturing.
In chemical industry, it is widely used in manufacturing vacuum, distilling pot, brewing pot etc. In the defense industry, it is used to manufacture bullets, cannonballs, gun parts and so on. For every 3 million rounds of ammunition, 13 ~ 14 tons of copper are needed. In the construction industry, the use of various pipes, pipe fittings, decorative devices, etc.
In medicine, copper's bactericidal action is long recognized. Copper has been found to have a very good medicinal use since the 1950s. Inventor Liu Tongqing Chinese medicine study found that in the 1970 s, copper with strong anti-cancer function, and successfully developed the corresponding anticancer drugs "7851 grams of cancer", success in clinic. Later, Mexican scientists also discovered that copper has anti-cancer properties. In the new century, British researchers also found that copper has a strong bactericidal effect. In the near future, the copper element will make a great contribution to the improvement of human health.