- Copper (Cu) is a reddish-orange, highly ductile and malleable transition metal with atomic number 29, positioned in Group 11 of the periodic table.
- It has eleven valence electrons—one in the 4s subshell and ten in the 3d subshell—and commonly exhibits oxidation states of +1 (cuprous) and +2 (cupric), though oxidation states from 0 to +4 are known in specific compounds. Its atomic structure consists of twenty-nine protons, typically thirty-five neutrons, and twenty-nine electrons arranged in four shells.
- Naturally occurring copper consists of two stable isotopes: copper-63 (⁶³Cu), which makes up about 69.17%, and copper-65 (⁶⁵Cu), comprising about 30.83%.
- Copper is relatively abundant in Earth’s crust, occurring at about 50 parts per million. It is found both in its native metallic form and in various ores, the most important of which include chalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), chalcocite (Cu₂S), cuprite (Cu₂O), malachite (Cu₂CO₃(OH)₂), and azurite (Cu₃(CO₃)₂(OH)₂). Large deposits exist in Chile, Peru, China, the Democratic Republic of the Congo, and the United States. Native copper is also found in certain geological settings, such as the Keweenaw Peninsula in Michigan, USA.
- Copper is one of the first metals used by humans, with archaeological evidence of copper use dating back at least 10,000 years. The discovery of smelting techniques around 5000 BCE allowed the extraction of copper from ores, ushering in the Chalcolithic (“Copper Age”). The alloying of copper with tin to make bronze marked the start of the Bronze Age around 3300 BCE. The name “copper” comes from the Latin cuprum, itself derived from aes Cyprium (“metal of Cyprus”), reflecting the island’s historical importance as a copper source.
- Copper is valued for its excellent electrical and thermal conductivity—second only to silver among pure metals—making it indispensable in electrical wiring, motors, transformers, and printed circuit boards. It is also widely used in plumbing, roofing, heat exchangers, and industrial machinery. Copper alloys have significant applications: brass (copper–zinc) is used in musical instruments and decorative items, while bronze (copper–tin) is used in sculptures, coins, and engineering components.
- Chemically, copper is moderately reactive. It does not react with water but slowly oxidizes in moist air to form a dull brown oxide layer, which can further transform into a characteristic green patina of basic copper carbonate (Cu₂(OH)₂CO₃) in the presence of carbon dioxide and moisture. This patina is protective, preventing further corrosion, and is often valued for its aesthetic appeal, as seen on the Statue of Liberty.
- Biologically, copper is an essential trace element required by all plants and animals. In humans, it plays a role in enzymes involved in iron metabolism, connective tissue formation, and neurotransmitter synthesis. The human body contains about 50–120 mg of copper, primarily in the liver, brain, heart, and kidneys. Dietary deficiency can cause anemia, bone abnormalities, and immune dysfunction, while excessive intake can be toxic, leading to liver and kidney damage.
- Copper compounds have diverse uses: copper(II) sulfate (CuSO₄·5H₂O) is widely used in agriculture as a fungicide and algicide, in electroplating, and in chemical education; copper-based pigments are used in paints, ceramics, and glass; and copper catalysts play roles in organic synthesis and petrochemical refining.
- Environmentally, copper is both vital and potentially harmful. While trace amounts are essential for life, excessive concentrations from mining, smelting, or industrial discharge can contaminate soil and water, harming aquatic life. Copper recycling is highly efficient and economically viable, with over 30% of global demand met from recycled sources, reducing environmental impact and conserving resources.
