The Copper reference article from the English Wikipedia on 24-Jul-2004
(provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Copper

Learn about Africa online
nickelcopperzinc
Cu
Ag  
 
 
Image:Cu-TableImage.png
General
Name, Symbol, Numbercopper, Cu, 29
Chemical series transition metals
Group, Period, Block11, 4 , d
Density, Hardness 8920 kg/m3, 3.0
Appearance copper, metallic
125px
Atomic properties
Atomic weight 63.536 amu
Atomic radius (calc.) 135 (145) pm
Covalent radius 138 pm
van der Waals radius 140 pm
Electron configuration [Ar]3d3d104s1
e- 's per energy level2, 8, 18, 1
Oxidation states (Oxide) 2,1 (mildly basic)
Crystal structure cubic, face-centered
Physical properties
State of matter solid (__)
Melting point 1357.6 K (1984.3 ðF)
Boiling point 2840 K (4653 ðF)
Molar volume 7.11 ×1010-6 m3/mol
Heat of vaporization 300.3 kJ/mol
Heat of fusion 13.05 kJ/mol
Vapor pressure 0.0505 Pa at 1358 K
Speed of sound 3570 m/s at 293.15 K
Miscellaneous
Electronegativity 1.9 (Pauling scale)
Specific heat capacity 380 J/(kg*K)
Electrical conductivity 59.6 106/m ohm
Thermal conductivity 401 W/(m*K)
1st ionization potential 745.5 kJ/mol
2nd ionization potential 1957.9 kJ/mol
3rd ionization potential 3555 kJ/mol
4th ionization potential 5536 kJ/mol
Most stable isotopes
isoNAhalf-life DMDE MeVDP
63Cu69.17%Cu is stable with 34 neutrons
64Cu{syn.}12.7 h &epsilon1.67564Ni
64Cu{syn.}12.7 h β-0.57964Zn
65Cu30.83%Cu is stable with 36 neutrons
SI units & STP are used except where noted.

Copper is a chemical element in the periodic table that has the symbol Cu and atomic number 29.

Table of contents
1 Notable characteristics
2 Applications
3 History
4 Biological role
5 Occurrence
6 Compounds
7 Isotopes
8 Precautions
9 Reference
10 External links

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:

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. In Europe, Oetzi the Iceman, a well preserved male dated to 3200 BCE, was found with a copper tipped axe whose metal was 99.7% pure. High levels of arsenic in his hair suggests he was involved in copper smelting.

The use of bronze was so pervasive in a certain era of civilization that it has been named the Bronze Age. The transitional period in certain regions between the preceding Neolithic period and the Bronze Age is termed the Chalcolithic, with some high purity copper tools being used alongside stone tools.

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

Alchemical symbol for copper
was associated with the goddess Aphrodite/Venus in mythology and alchemy, owing to its lustrous beauty, its ancient use in producing mirrors, and its association with Cyprus, which was sacred to the goddess. In alchemy, the symbol for copper was also the symbol for the planet Venus.

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 blood of the horseshoe crab, Limulus polyphemus uses copper rather than iron for oxygen transport.

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 is not 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 copper (I) state, Cu+1, and copper (II) 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 (YBa2Cu3O7-δ) or YBCO) form the basis of many unconventional superconductors

Other compounds : copper (II) 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.

Reference

External links