Copper Cu

Discovery

Copper occurs naturally as pure metal, so it was among the first metals people shaped. Copper ornaments from the Middle East date back roughly ten thousand years, hammered from native copper. Around the fifth millennium BCE people learned to smelt copper from its ores, and later discovered that adding tin produced bronze, a harder alloy that gave its name to the Bronze Age, beginning in the Near East around 3300 BCE.

The island of Cyprus was a major source of copper for the Mediterranean world, and the Romans obtained much of their copper there. Copper and its alloys were used for tools, weapons, coins, mirrors and plumbing.

In the nineteenth century, the telegraph and then electric power and telephone networks created enormous demand for copper wire, and electrolytic refining produced the high-purity copper needed for good conductivity.

Origin of the name

The Romans called the metal aes Cyprium, 'metal of Cyprus', later shortened to cyprum and then cuprum, which gives the symbol Cu. The English word copper comes from the same Latin source.

Main uses

• Electrical wiring: building wiring, power cables, transformers and motor windings account for the largest share of copper use.
• Electronics: printed circuit boards and chip interconnects rely on copper.
• Plumbing and heat transfer: copper pipes, radiators, air-conditioning coils and heat exchangers.
• Alloys: brass (copper and zinc) is used in fittings and musical instruments, bronze (copper and tin) in bearings and sculpture, and cupronickel in coins.
• Electric vehicles and renewables: electric cars, wind turbines and solar installations use considerably more copper than their conventional counterparts.

Isotopes

Copper has two stable isotopes: copper-63 (about 69 percent) and copper-65 (about 31 percent). Of its radioactive isotopes, copper-64, with a half-life of about 12.7 hours, is used in PET imaging and studied for therapy, and copper-67, with a half-life of about 2.6 days, is being investigated for targeted cancer treatment.

In everyday life

Copper is an essential trace element. It is part of enzymes that help the body use iron, produce energy in cells and build connective tissue. Shellfish, nuts, seeds, whole grains and organ meats are good sources. In the inherited condition Wilson's disease the body cannot remove excess copper, which builds up in the liver and brain.

Octopuses, squid and horseshoe crabs have blue blood because their oxygen carrier, haemocyanin, contains copper instead of iron. Copper surfaces also kill many microbes over time.