Copper

Copper is one of the oldest metals known to humans, it was being shaped into tools and ornaments over 11,000 years ago. Today it is the metal that carries almost all the electricity in the world: from the power station through cables in your walls to the circuit board in your phone, copper is the wire that keeps modern civilisation running.

  • Atomic Number2929 protons, 29 electrons
  • Atomic Mass63.55 uAbout 64× heavier than hydrogen
  • State at Room TempSoliddistinctive orange-red metal
  • Density8.933 g/cm³About 9× denser than water
  • Melting / Boiling1084.6°C / 2561.8°CMelts at 1,085°C
  • DiscoveredAncientKnown since 9,000 BCE

How does copper compare to other common electrical conductors?

Copper is the best non-precious metal conductor of electricity. Silver is better but far more expensive.

Electrical Conductivity Comparison (MS/m)
Silver62.1
Copper59.6
Gold45.2
Aluminium37.7
Iron10.2

Copper conducts electricity approx. 97% as well as silver: the best conductor, but at a tiny fraction of the cost. Aluminium conducts only 60% as well as copper but weighs three times less, making it preferred for long overhead power lines.

What is copper?

Copper is a transition metal in Group 11 of the periodic table. It has 29 protons and a distinctive orange-red colour, unlike most metals, which are grey or silver. This warm colour comes from the way copper's electron structure interacts with light. Copper is an excellent conductor of heat and electricity, second only to silver among all elements. It is soft, ductile and can be drawn into very thin wire without breaking. Pure copper does not rust, but it slowly forms a green patina (copper carbonate) when exposed to air and moisture over years.

Copper gets its name from the island of Cyprus (Kypros in Greek), which was a major source of copper in the ancient world. The Latin name was cuprum, giving the chemical symbol Cu. Cyprus was so associated with copper that the element was sometimes called "Cyprian metal". Copper artefacts found in Iraq date back to around 9000 BCE, making it one of the earliest metals worked by humans.

Fact The Statue of Liberty is made of copper, approx. 80 tonnes of it in sheets just 2.4 mm thick, hammered into shape and attached to an iron framework. When it was unveiled in 1886, it was a shiny reddish-brown. Over the following decades it slowly turned the distinctive blue-green colour we see today, as the copper reacted with air and moisture to form a layer of copper carbonate: the same green patina that appears on old copper roofs and statues worldwide.

Where you find copper

On Earth

Copper is one of the few metals found in significant quantities as a free element, native copper, as well as in ores.

  • Chalcopyrite (CuFeS₂). The most important copper ore, a brass-coloured sulfide mineral. Chile holds approx. 28% of the world's copper reserves, making it by far the largest copper producer.
  • Malachite and azurite. Striking green and blue copper carbonate minerals found in the upper, weathered zones of copper deposits. Malachite was used as a green pigment and ornamental stone for thousands of years.
  • Native copper. Chunks of pure copper metal occur naturally in some locations, most famously around Lake Superior in North America, where indigenous peoples collected it thousands of years ago.

How we use copper

  • Electrical wiring. About 65% of all copper goes into electrical applications. Every building, every appliance and every electronic device contains copper wiring. The global electricity grid is essentially a copper network.
  • Plumbing. Copper pipes are used for water supply and central heating because copper does not corrode in water and naturally inhibits bacterial growth.
  • Bronze and brass. Bronze (copper-tin alloy) and brass (copper-zinc alloy) are two of the most important alloys in human history, used since ancient times for tools, weapons, coins and musical instruments.
  • Antimicrobial surfaces. Copper kills most bacteria and viruses within hours of contact. Copper door handles, railings and hospital surfaces reduce the spread of infection, a property recognised before the germ theory of disease.
Did you know? Copper is naturally antimicrobial, bacterial and viral cells are rapidly killed on copper surfaces. Research during the Covid-19 pandemic found that SARS-CoV-2 remained viable for up to 72 hours on plastic and stainless steel but was inactivated within 4 hours on copper. Hospitals that have replaced steel and plastic surfaces with copper have seen significant reductions in infection rates.

How it was discovered

Copper has been used since at least 9000 BCE, predating writing, the wheel and most other human technologies. The transition from the Stone Age to the Copper Age (Chalcolithic period) occurred gradually across different cultures. The discovery of bronze, copper alloyed with tin, around 3300 BCE began the Bronze Age, one of the most transformative periods in human prehistory. Copper has been mined, smelted and traded continuously for over 10,000 years, longer than any other metal.

Deeper dive: copper in biology and electrical applications

Copper is essential for life. It is needed for many enzymes, including cytochrome c oxidase (a key enzyme in cellular respiration) and superoxide dismutase (which protects cells from oxidative damage). Copper is involved in producing melanin (the pigment in skin and hair), forming connective tissue and making red blood cells. Some animals, octopuses, lobsters and horseshoe crabs, use copper-containing haemocyanin instead of iron-containing haemoglobin to carry oxygen, giving their blood a blue-green colour.

The extraordinary electrical conductivity of copper arises from the quantum mechanical behaviour of its electrons. Copper atoms have one loosely held outer electron that is essentially free to move through the metal lattice, these "sea of electrons" carry electrical current with very little resistance. Any impurity or crystal defect disrupts this movement, which is why electrical-grade copper must be 99.9% pure. Refining copper to this purity level is done by electrolysis, dissolving impure copper at an anode and depositing pure copper at a cathode.

As the world electrifies, with more electric vehicles, renewable energy generation and smart grids, demand for copper is projected to more than double by 2050. Copper is non-renewable on human timescales but is almost infinitely recyclable; recycled copper requires only 10% of the energy of newly smelted copper.

Copper is the metal of civilisation, from the Bronze Age to the electric age, it has been indispensable. Moving to 30 protons brings us to zinc, the metal that protects iron from rust and is essential for your immune system.