Copper is a chemical element; it has symbol Cu (from Latin: cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, and constantan used in strain gauges and thermocouples for temperature measurement.
|Appearance||Red-orange metallic luster|
|Standard atomic weight Ar°(Cu)|
|Copper in the periodic table|
|Atomic number (Z)||29|
|Electron configuration||[Ar] 3d10 4s1|
|Electrons per shell||2, 8, 18, 1|
|Phase at STP||solid|
|Melting point||1357.77 K (1084.62 °C, 1984.32 °F)|
|Boiling point||2835 K (2562 °C, 4643 °F)|
|Density (near r.t.)||8.96 g/cm3|
|when liquid (at m.p.)||8.02 g/cm3|
|Heat of fusion||13.26 kJ/mol|
|Heat of vaporization||300.4 kJ/mol|
|Molar heat capacity||24.440 J/(mol·K)|
|Oxidation states||−2, 0, +1, +2, +3, +4 (a mildly basic oxide)|
|Electronegativity||Pauling scale: 1.90|
|Atomic radius||empirical: 128 pm|
|Covalent radius||132±4 pm|
|Van der Waals radius||140 pm|
|Spectral lines of copper|
|Crystal structure||face-centered cubic (fcc)|
|Speed of sound thin rod||(annealed)|
3810 m/s (at r.t.)
|Thermal expansion||16.5 µm/(m⋅K) (at 25 °C)|
|Thermal conductivity||401 W/(m⋅K)|
|Electrical resistivity||16.78 nΩ⋅m (at 20 °C)|
|Molar magnetic susceptibility||−5.46×10−6 cm3/mol|
|Young's modulus||110–128 GPa|
|Shear modulus||48 GPa|
|Bulk modulus||140 GPa|
|Vickers hardness||343–369 MPa|
|Brinell hardness||235–878 MPa|
|Naming||after Cyprus, principal mining place in Roman era (Cyprium)|
|Discovery||Middle East (9000 BC)|
|Symbol||"Cu": from Latin cuprum|
|Isotopes of copper|
Copper is one of the few metals that can occur in nature in a directly usable metallic form (native metals). This led to very early human use in several regions, from c. 8000 BC. Thousands of years later, it was the first metal to be smelted from sulfide ores, c. 5000 BC; the first metal to be cast into a shape in a mold, c. 4000 BC; and the first metal to be purposely alloyed with another metal, tin, to create bronze, c. 3500 BC.
In the Roman era, copper was mined principally on Cyprus, the origin of the name of the metal, from aes cyprium (metal of Cyprus), later corrupted to cuprum (Latin). Coper (Old English) and copper were derived from this, the later spelling first used around 1530.
Commonly encountered compounds are copper(II) salts, which often impart blue or green colors to such minerals as azurite, malachite, and turquoise, and have been used widely and historically as pigments.
Copper used in buildings, usually for roofing, oxidizes to form a green patina of compounds called verdigris. Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as bacteriostatic agents, fungicides, and wood preservatives.
Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the iron-complexed hemoglobin in fish and other vertebrates. In humans, copper is found mainly in the liver, muscle, and bone. The adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight.