Definition: Copper is a chemical element in the periodic table that has the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with excellent electrical conductivity, and finds extensive use as an electrical conductor, heat conductor, as a building material, and as a component of various alloys.

Copper is an essential trace nutrient to all high plants and animals. In animals, including humans, it is found primarily in the bloodstream, as a co-factor in various enzymes, and in copper-based pigments. However, in sufficient amounts, copper can be poisonous and even fatal to organisms.

Copper has played a significant part in the history of mankind, which has used the easily accessible uncompounded metal for nearly 10,000[citation needed] years. Civilizations in places such as Iraq, China, Egypt, Greece and the Sumerian cities all have early evidence of using copper. During the Roman Empire, copper was principally mined on Cyprus, hence the origin of the name of the metal as Cyprium, "metal of Cyprus", later shortened to Cuprum. A number of countries, such as Chile and the United States, still have sizable reserves of the metal which are extracted through large open pit mines. Nevertheless, the price of copper has risen rapidly, increasing 500% from a 60-year low in 1999, largely due to increased demand. The Earth has an estimated 61 years of copper reserves remaining.

 

Conductivity
Copper has a high electrical and thermal conductivity, second only to silver among pure metals at room temperature.

Colour
Copper is a reddish-colored metal; it has its characteristic color because it reflects red and orange light and absorbs other frequencies in the visible spectrum, due to its band structure.

In its liquefied state, a pure copper surface without ambient light appears somewhat greenish, a characteristic shared with gold. When liquid copper is in bright ambient light, it retains some of its pinkish luster.

Location in the periodic table
Copper occupies the same family of the periodic table as silver and gold, since they each have one s-orbital electron on top of a filled electron shell. This similarity in electron structure makes them similar in many characteristics. All have very high thermal and electrical conductivity, and all are malleable metals.

Corrosion properties

Pure water and air
Copper is a metal that does not react with water (H2O), but the oxygen of the air will react slowly at room temperature to form a layer of copper oxide on copper metal.

It can be seen that copper in "pure" water is more noble than hydrogen. As a result it does not corrode in oxygen free water and the corrosion rate in oxygenated water is low.

The Pourbaix diagram for copper in pure water, perchloric acid or sodium hydroxide. It is important to note that in contrast to the oxidation of iron by wet air that the layer formed by the reaction of air with copper has a protective effect against further corrosion. On old copper roofs a green layer of copper carbonate can often be seen.

Sulphide media
Copper metal does react with hydrogen sulphide and sulfide containing solutions. A series of different copper sulphides can form on the surface of the copper metal.

 

Applications

Native copper specimen (~ 4 cm in size)Copper is malleable and ductile, a good conductor of heat and, when very pure, a good conductor of electricity.

The purity of copper is expressed as 4N for 99.99% pure or 7N for 99.99999% pure. The numeral gives the number of nines after the decimal point when expressed as a decimal (e.g. 4N means 0.9999, or 99.99%).

It is used extensively, in products such as:

Piping
including, but not limited to, extreme water supply.

Electronics
Copper wire.
Electromagnets.
Printed circuit boards.
Lead free solder, alloyed with tin.
Electrical machines, especially electromagnetic motors, generators and transformers.
Electrical relays, electrical busbars and electrical switches.
Vacuum tubes, cathode ray tubes, and the magnetrons in microwave ovens.
Wave guides for microwave radiation.
Integrated circuits, increasingly replacing aluminium because of its superior electrical conductivity.
As a material in the manufacture of computer heat sinks, as a result of its superior heat dissipation capacity to aluminium.

Architecture
Copper has been used as water-proof roofing material since ancient times, giving many old buildings their greenish roofs and domes. Initially copper oxide forms, replaced by cuprous and cupric sulfide, and finally by copper sulfate. The final sulfate patina is highly resistant to corrosion.
Statuary: The Statue of Liberty, for example, contains 179,220 pounds (81.3 tonnes) of copper.
Alloyed with nickel, e.g. cupronickel and Monel, used as corrosive asistant materials in shipbuilding.
Watt's steam engine.

Household Products
Copper plumbing fittings and compression tubes.
Doorknobs and other fixtures in houses.
Roofing, guttering, and rainspouts on buildings.
In cookware, such as frying pans.
Most flatware (knives, forks, spoons) contains some copper (nickel silver).
Sterling silver, if it is to be used in dinnerware, must contain a few percent copper.
Copper water heating cylinders

Coinage
As a component of coins, often as cupronickel alloy.
Coins in the following countries all contain copper: European Union (Euro),[6] United States,[7] UnitedKingdom (sterling),[8] Australia[9] and New Zealand.[10]
Ironically, U.S. Nickels are 75.0% copper by weight and only 25.0% nickel.[7]

Biomedical applications
As a biostatic surface in hospitals, and to line parts of ships to protect against barnacles and mussels, originally used pure, but superseded by Muntz Metal. Bacteria will not grow on a copper surface because it is biostatic. Copper doorknobs are used by hospitals to reduce the transfer of disease, and Legionnaires' disease is suppressed by copper tubing in air-conditioning systems.
Copper(II) sulfate is used as a fungicide and as algae control in domestic lakes and ponds. It is used in gardening powders and sprays to kill mildew.
Copper-62-PTSM, a complex containing radioactive copper-62, is used as a Positron emission tomography radiotracer for heart blood flow measurements.
Copper-64 can be used as a Positron emission tomography radiotracer for medical imaging. When complexed with a chelate it can be used to treat cancer through radiation therapy.

Chemical applications
Compounds, such as Fehling's solution, have applications in chemistry.
As a component in ceramic glazes, and to color glass.