Copper

Notable Characteristics

Copper is a reddish-coloured metal, with a high electrical and thermal conductivity (among pure metals at room temperature, only silver has a higher electrical conductivity). Copper may well be the oldest metal in use, as copper artifacts dating to 8700 BC have been found. Besides being part of various ores, copper can be found in the metallic form ( i.e. native copper) in some locations.

In Greek times, the metal was known by the name Chalkos. In Roman times, it became known as aes Cyprium, because so much of it was mined in Cyprus. From this, the phrase was simplified to cuprum and then Anglicized into the English copper.

Applications

Copper is malleable and ductile, and is used extensively, in products such as:

• Copper wire.
• Copper plumbing.
• Doorknobs and other fixtures in houses.
• Statuary[?]: The Statue of Liberty, for example, contains 179,000 pounds of copper.
• Electromagnets.
• Motors, esp electromagnetic motors.
• Watt's steam engine.
• Electrical relays and electrical switches.
• Vacuum tubes, cathode ray tubes, and the magnetrons in microwave ovens.
• Wave guides for microwave radiation.
• There is increasing use of copper in integrated circuits, replacing aluminum because of its superior conductivity.
• As a component of coins.
• 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.
• As a component in ceramic glazes, and to color glass.
• Musical instruments, especially brass instruments.
• As a biostatic[?] surface in hospitals, and to line parts of ships to protect against barnacles and mussels.
• Compounds, such as Fehling's solution[?], have applications in chemistry.
• Copper sulfate[?] is used as a poison and a water purifier.

History

Copper was known to some of the oldest civilizations on record, and has a history of use that is at least 10,000 years old. A copper pendant was found in what is now northern Iraq that dates to 8700 BC. By 5000 BC there are signs of copper smelting, the refining of copper from simple copper oxides such as malachite[?] or azurite[?]. The earliest signs of gold use, by contrast, appear around 4000 BC.

There are copper and bronze artifacts from Sumerian cities that date to 3000 BC, and Egyptian artifacts in copper and copper alloyed with tin nearly as old. In one pyramid, a copper plumbing system was found that is 5000 years old. The Egyptians found that adding a small amount of tin made the metal easier to cast, so bronze alloys are found in Egypt almost as soon as copper is found. Use of copper in ancient China dates to at least 2000 BC. By 1200 BC excellent bronzes were being made in China. Note that these dates are affected by wars and conquest, as copper is easily melted down and reused.

The use of bronze was so pervasive in a certain era of civilization that it has been named the Bronze Age.

Brass was known to the Greeks but first used extensively by the Romans.

Biological Role

Copper is essential in all higher plants and animals. Copper is found in a variety of enzymes, including the copper centers of cytochrome c oxidase, the Cu-Zn containing enzyme superoxide dismutase, and is the central metal in the oxygen carrying pigment hemocyanin. The RDA for copper in normal healthy adults is 0.9 mg/day.

Copper is carried mostly in the bloodstream on a plasma protein[?] called ceruloplasmin[?]. Though when copper is first absorbed in the gut it is transported to the liver bound to albumin.

An inherited condition called Wilson's disease causes the body to retain copper, as it isn't excreted by the liver into the bile. This disease, if untreated, can lead to brain and liver damage.

Occurrence

Copper is usually found in a mineral form. Minerals such as azurite[?], malachite[?] and bornite[?] are sources of copper, as are sulfides such as chalcopyrite (CuFeS2), coveline[?] (CuS), chalcosine[?] (Cu2S) or oxides like cuprite[?] (Cu2O).

Compounds

There are numerous alloys of copper - Brass is a copper/zinc alloy, and bronze is a copper/tin alloy.

Common oxidation states of copper include the cuprous state, Cu⁺¹, and cupric state, Cu⁺².

Copper carbonate is green from which arises the unique appearance of copper-clad roofs or domes on some buildings.

Copper oxides (e.g. yttrium barium copper oxide (YBa₂Cu₃O_7-δ) or YBCO[?]) form the basis of many unconventional superconductors

Other compounds : copper sulfide

Isotopes

There are two stable isotopes, ⁶³Cu and ⁶⁵Cu, along with a couple dozen radioisotopes. The vast majority of radioisotopes have half lives on the order of minutes or less, the longest lived, ⁶⁴Cu, has a half life of 12.7 hours, with two decay modes, leading to two separate products.

Precautions

All copper compounds, unless otherwise known, should be treated as if they were toxic.The metal, when powdered, is a fire hazard. 30g of copper sulfate is potentially lethal in humans. Copper in drinking water at concentrations higher than 1 mg/liter can stain clothes and items washed in water. The suggested safe level of copper in drinking water for humans varies depending on the source, but tends to be pegged at 1.5 to 2 mg/liter.

External Links

• WebElements.com - Copper (http://www.webelements.com/webelements/elements/text/Cu/index.html)
• EnvironmentalChemistry.com - Copper (http://environmentalchemistry.com/yogi/periodic/Cu.html)
• The Copper Page (http://www.copper.org/)

Common misspelling and questions (FAQ)

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