copper

copper
Number	29
Category	transition metal

copper. A chemical element with the symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface has a reddish-orange color, and it has been used for millennia as a conductor, in building materials, and as a component of various alloys, such as brass and bronze.

Properties

Copper, along with gold and caesium, is one of the few metallic elements with a distinct color other than silver or gray. It exhibits excellent electrical conductivity, second only to silver among pure metals at room temperature, which is why it is the international standard for electrical conductors. Its high thermal conductivity makes it valuable in heat exchangers, as seen in heating, ventilation, and air conditioning systems and computer heat sinks. The metal is face-centered cubic in structure and is relatively inert, forming a protective layer of copper oxide and basic copper carbonate (patina) when exposed to the atmosphere, which gives structures like the Statue of Liberty its characteristic green color. Key compounds include copper(II) sulfate, used in agriculture and as a reagent, and copper(I) oxide, a component in antifouling paint.

Occurrence and production

Native copper occurs in various mineral forms, often in basalt cavities, with major deposits historically found on the Keweenaw Peninsula in Michigan and in Corocoro, Bolivia. The largest known single mass of native copper was discovered in 1857 on the Keweenaw Peninsula. Economically significant ores include chalcopyrite and bornite, often found in porphyry copper deposits like those mined at the Chuquicamata mine in Chile and the Grasberg mine in Indonesia. Major producers are Chile, Peru, and the People's Republic of China. Production primarily involves mining, followed by concentration, smelting, and electrorefining, often at large facilities operated by companies like Freeport-McMoRan and BHP. A significant portion of supply comes from recycling scrap.

History

Copper use dates to the Neolithic period, with a copper pendant from Shanidar Cave dating to around 8700 BCE. The Chalcolithic, or Copper Age, saw its use for tools and ornaments, as evidenced in sites like the Vinča culture. The metal was crucial to ancient civilizations, including those in Ancient Egypt, where it was used for water piping in the Pyramid of Djoser, and in Sumer, as seen in artifacts from the Royal Cemetery at Ur. The Bronze Age began with the creation of bronze, an alloy with tin, revolutionizing tool and weapon making across Mesopotamia, the Indus Valley Civilisation, and Minoan civilization. The Romans extensively mined copper from Cyprus, from which the metal's name is derived, using it for coinage, architecture, and military equipment like those used by the Roman legion.

Applications

Approximately half of all copper produced is used for electrical wiring and cabling in power generation, telecommunications, and electronics. It is essential in electric motors, transformers, and the integrated circuits of devices from smartphones to the International Space Station. In construction, it is used for roofing, plumbing, and rain gutters due to its durability, seen in landmarks like the Hindu temple at Tanjore. Alloys are widespread: brass is used for musical instruments like trumpets and for decorative art, while bronze is used for sculpture, bearings, and marine hardware. Copper compounds serve as fungicides in agriculture, pigments like Egyptian blue, and catalysts in chemical processes such as the Wacker process.

Biological role

Copper is an essential trace element for all living organisms, functioning as a cofactor for numerous enzymes known as cuproenzymes. In humans, these include cytochrome c oxidase, crucial for cellular respiration in the mitochondrion, and superoxide dismutase, an important antioxidant. The transport protein ceruloplasmin carries copper through the bloodstream, while ATP7A and ATP7B regulate its cellular metabolism; mutations in ATP7B cause Wilson's disease. In marine life, the blood of some arthropods, like the horseshoe crab, and mollusks, such as the octopus, contains the copper-based protein hemocyanin for oxygen transport, giving their blood a blue color.

Health and safety

While essential, excess copper is toxic. Acute ingestion can cause gastrointestinal distress, and chronic exposure, as seen in conditions like Wilson's disease, leads to copper accumulation in the liver and brain. Occupational exposure to copper dust or fumes, regulated by agencies like the Occupational Safety and Health Administration, can cause metal fume fever. The Environmental Protection Agency sets limits for copper in drinking water, as high levels can be harmful, particularly to individuals with Menkes disease. Copper surfaces have intrinsic antimicrobial properties, a characteristic leveraged in hospitals on touch surfaces to reduce the transmission of pathogens like Methicillin-resistant Staphylococcus aureus and Escherichia coli.

Category:Chemical elements Category:Transition metals