Copper

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Copper,29Cu

Native copper (~4 cm in size)

General properties

Name,symbolcopper, Cu

Pronunciation/

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Appearancered-orange metallic luster

Copper in theperiodic table

CuAgnickelcopperzinc

Atomic number29

Standard atomic weight()63.546(3)[1]

Element categorytransition metal

Group,blockgroup11,d-block

Periodperiod4

Electron configuration[Ar] 3d104s1

per shell2, 8, 18, 1

Physical properties

Phasesolid

Meltingpoint1357.77K(1084.62C, 1984.32F)

Boilingpoint2835K (2562C, 4643F)

Densitynearr.t.8.96gcm3

whenliquid, atm.p.8.02gcm3

Heatoffusion13.26kJmol1

Heat of vaporization300.4kJmol1

Molar heat capacity24.440Jmol1K1

vaporpressureP(Pa)

1

10

100

1k

10k

100k

atT(K)

1509

1661

1850

2089

2404

2834

Atomic properties

Oxidation states+1,+2, +3, +4(a mildlybasicoxide)

ElectronegativityPaulingscale: 1.90

Ionization energies1st:745.5kJmol12nd:1957.9kJmol13rd:3555kJmol1(more)

Atomic radiusempirical: 128pm

Covalent radius1324pm

Van der Waals radius140pm

Miscellanea

Crystal structureface-centeredcubic(fcc)

Speed of soundthinrod(annealed)3810ms1(atr.t.)

Thermal expansion16.5mm1K1(at25C)

Thermal conductivity401Wm1K1

Electrical resistivity16.78nm (at20C)

Magnetic orderingdiamagnetic[2]

Young's modulus110128GPa

Shear modulus48GPa

Bulk modulus140GPa

Poisson ratio0.34

Mohs hardness3.0

Vickers hardness343369MPa

Brinell hardness235878MPa

CAS Registry Number7440-50-8

History

NamingafterCyprus, principal mining place in Roman era (Cyprium)

DiscoveryMiddle East(9000 BCE)

Most stable isotopes

Main article:Isotopes of copper

isoNAhalf-lifeDMDE(MeV)DP63Cu

69.15%

63Cu isstablewith 34neutrons64Cusyn12.700h

64Ni

64Zn65Cu

30.85%

65Cu is stable with 36 neutrons

67Cu

syn

61.83h

67Zn

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Copperis achemical elementwith symbolCu(fromLatin:cuprum) andatomic number29. It is aductilemetal with very highthermalandelectrical conductivity. Pure copper is soft and malleable; a freshly exposed surface has a reddish-orange color. It is used as a conductor of heat and electricity, a building material, and a constituent of various metalalloys.

The metal andits alloyshave been used for thousands of years. In the Roman era, copper was principally mined onCyprus, hence the origin of the name of the metal asyprium(metal of Cyprus), later shortened touprum. Its compounds are commonly encountered as copper(II) salts, which often impart blue or green colors to minerals such asazuriteandturquoiseand have been widely used historically as pigments. Architectural structures built with copper corrode to give greenverdigris(orpatina).Decorative artprominently features copper, both by itself and as part of pigments.

Copper is essential to all living organisms as a tracedietary mineralbecause it is a key constituent of the respiratory enzyme complexcytochrome c oxidase. Inmolluscsandcrustaceacopper is a constituent of the blood pigmenthemocyanin, which is replaced by the iron-complexedhemoglobinin fish and othervertebrates. The main areas where copper is found in humans are liver, muscle and bone.[3]Copper compounds are used asbacteriostatic substances,fungicides, and wood preservatives.

Contents

[hide] 1Characteristics 1.1Physical 1.2Chemical 1.3Isotopes 1.4Occurrence 2Production 2.1Reserves 2.2Methods 2.3Recycling 3Alloys 4Compounds 4.1Binary compounds 4.2Coordination chemistry 4.3Organocopper chemistry 4.4Copper(III) and copper(IV) 5History 5.1Copper Age 5.2Bronze Age 5.3Antiquity and Middle Ages 5.4Modern period 6Applications 6.1Wire and cable 6.2Electronics and related devices 6.3Electric motors 6.4Architecture 6.5Antibiofouling applications 6.6Antimicrobial applications 6.7Folk medicine 6.7.1Compression Clothing 6.8Other uses 7Degradation 8Biological role 8.1Dietary needs 8.2Copper-based disorders 9See also 10References 11Notes 12Further reading 13External linksCharacteristicsPhysical

A copper disc (99.95% pure) made bycontinuous casting;etchedto revealcrystallites.

Copper just above its melting point keeps its pink luster color when enough light outshines the orangeincandescencecolor.

Copper,silverandgoldare ingroup 11of the periodic table, and they share certain attributes: they have one s-orbital electron on top of a filled d-electron shelland are characterized by high ductility and electrical conductivity. The filled d-shells in these elements do not contribute much to the interatomic interactions, which are dominated by the s-electrons throughmetallic bonds. Unlike in metals with incomplete d-shells, metallic bonds in copper are lacking acovalentcharacter and are relatively weak. This explains the lowhardnessand highductilityof single crystals of copper.[4]At the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is usually supplied in a fine-grainedpolycrystallineform, which has greater strength thanmonocrystallineforms.[5]The softness of copper partly explains its high electrical conductivity (59.6106S/m) and thus also high thermal conductivity, which are the second highest among pure metals at room temperature.[6]This is because the resistivity to electron transport in metals at room temperature mostly originates from scattering of electrons on thermal vibrations of the lattice, which are relatively weak for a soft metal.[4]The maximum permissible current density of copper in open air is approximately 3.1106A/m2of cross-sectional area, above which it begins to heat excessively.[7]As with other metals, if copper is placed against another metal,galvanic corrosionwill occur.[8]Together withcaesiumandgold(both yellow), andosmium(bluish), copper is one of only four elemental metals with a natural color other than gray or silver.[9]Pure copper is orange-red and acquires a reddishtarnishwhen exposed to air. The characteristic color of copper results from the electronic transitions between the filled 3d and half-empty 4s atomic shells the energy difference between these shells is such that it corresponds to orange light. The same mechanism accounts for the yellow color of gold and caesium.[4]Chemical

Unoxidized copper wire (left) and oxidized copper wire (right).

The East Tower of theRoyal Observatory, Edinburgh. The contrast between the refurbished copper installed in 2010 and the green color of the original 1894 copper is clearly seen.

Copper does not react with water but it does slowly react with atmospheric oxygen to form a layer of brown-black copper oxide which, unlike therustwhich forms when iron is exposed to moist air, protects the underlying copper from more extensive corrosion. A green layer ofverdigris(copper carbonate) can often be seen on old copper constructions such as theStatue of Liberty.[10]Coppertarnisheswhen exposed tosulfides, which react with it to form variouscopper sulfides.[11]IsotopesMain article:Isotopes of copperThere are 29isotopesof copper.63Cu and65Cu are stable, with63Cu comprising approximately 69% of naturally occurring copper; they both have aspinof32.[12]The other isotopes areradioactive, with the most stable being67Cu with ahalf-lifeof 61.83hours.[12]Sevenmetastable isotopeshave been characterized, with68mCu the longest-lived with a half-life of 3.8 minutes. Isotopes with amass numberabove 64 decay by, whereas those with a mass number below 64 decay by+.64Cu, which has a half-life of 12.7 hours, decays both ways.[13]62Cu and64Cu have significant applications.62Cu is used in62Cu-PTSM that is aradioactive tracerfor positron emission tomography.[14]Occurrence

Native copper from the Keweenaw Peninsula Michigan about 2.5 inches (6.4 cm) long

Copper is synthesized in massive stars[15]and is present in the Earth's crust at a concentration of about 50 parts per million (ppm),[16]where it occurs asnative copperor in minerals such as the copper sulfideschalcopyriteandchalcocite, the copper carbonatesazuriteandmalachite, and thecopper(I) oxidemineralcuprite.[6]The largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on theKeweenaw PeninsulainMichigan, US.[16]Native copper is apolycrystal, with the largest described single crystal measuring 4.43.23.2cm.[17]Production

Chuquicamatain Chile is one of the world's largestopen pitcoppermines.

World production trend

Copper prices 20032011 in USD per tonne

See also:List of countries by copper productionMost copper is mined orextractedas copper sulfides from largeopen pit minesinporphyry copperdeposits that contain 0.4 to 1.0% copper. Examples includeChuquicamatainChile,Bingham Canyon Minein Utah,United StatesandEl Chino Minein New Mexico, United States. According to theBritish Geological Survey, in 2005, Chile was the top mine producer of copper with at least one-third world share followed by the United States, Indonesia and Peru.[6]Copper can also be recovered through thein-situ leachprocess. Several sites in the state of Arizona are considered prime candidates for this method.[18]The amount of copper in use is increasing and the quantity available is barely sufficient to allow all countries to reach developed world levels of usage.[19]ReservesSee also:Peak copper ReservesCopper has been in use at least 10,000 years, but more than 95% of all copper ever mined andsmeltedhas been extracted since 1900,[20]and more than half was extracted in only the last 24 years. As with many natural resources, the total amount of copper on Earth is vast (around 1014tons just in the top kilometer of Earth's crust, or about 5 million years' worth at the current rate of extraction). However, only a tiny fraction of these reserves is economically viable, given present-day prices and technologies. Various estimates of existing copper reserves available for mining vary from 25 years to 60 years, depending on core assumptions such as the growth rate.[21]Recycling is a major source of copper in the modern world.[20]Because of these and other factors, the future of copper production and supply is the subject of much debate, including the concept ofpeak copper, analogous topeak oil.

The price of copper has historically been unstable,[22]and it sextupled from the 60-year low of US$0.60/lb (US$1.32/kg) in June 1999 to US$3.75 per pound (US$8.27/kg) in May 2006. It dropped to US$2.40/lb (US$5.29/kg) in February 2007, then rebounded to US$3.50/lb (US$7.71/kg) in April 2007.[23][bettersourceneeded]In February 2009, weakening global demand and a steep fall in commodity prices since the previous year's highs left copper prices at US$1.51/lb.[24]MethodsMain article:Copper extraction techniquesThe concentration of copper in ores averages only 0.6%, and most commercial ores are sulfides, especially chalcopyrite (CuFeS2) and to a lesser extent chalcocite (Cu2S).[25]These minerals are concentrated fromcrushedores to the level of 1015% copper byfroth flotationorbioleaching.[26]Heating this material with silica inflash smeltingremoves much of the iron as slag. The process exploits the greater ease of converting iron sulfides into its oxides, which in turn react with the silica to form the silicate slag, which floats on top of the heated mass. The resultingcopper matteconsisting of Cu2S is thenroastedto convert all sulfides into oxides:[25]2 Cu2S + 3 O2 2 Cu2O + 2 SO2The cuprous oxide is converted toblistercopper upon heating:

2 Cu2O 4 Cu + O2The Sudburymatteprocess converted only half the sulfide to oxide and then used this oxide to remove the rest of the sulfur as oxide. It was then electrolytically refined and the anode mud exploited for the platinum and gold it contained. This step exploits the relatively easy reduction of copper oxides to copper metal. Natural gas is blown across the blister to remove most of the remaining oxygen andelectrorefiningis performed on the resulting material to produce pure copper:[27]Cu2++ 2 e Cu

RecyclingLike aluminium, copper is 100% recyclable without any loss of quality, regardless of whether it is in a raw state or contained in a manufactured product. In volume, copper is the third most recycled metal after iron and aluminium. It is estimated that 80% of the copper ever mined is still in use today.[28]According to theInternational Resource Panel'sMetal Stocks in Society report, the global per capita stock of copper in use in society is 3555kg. Much of this is in more-developed countries (140300kg per capita) rather than less-developed countries (3040kg per capita).

The process of recycling copper is roughly the same as is used to extract copper but requires fewer steps. High-purity scrap copper is melted in a furnace and thenreducedand cast intobilletsandingots; lower-purity scrap is refined by electroplating in a bath of sulfuric acid.[29]AlloysSee also:List of copper alloysNumerouscopper alloysexist, many with important uses.Brassis an alloy of copper andzinc.Bronzeusually refers to copper-tinalloys, but can refer to any alloy of copper such asaluminium bronze. Copper is one of the most important constituents ofcaratsilver and gold alloys, and carat solders are used in the jewelry industry, modifying the color, hardness and melting point of the resulting alloys.[30]The alloy of copper and nickel, calledcupronickel, is used in low-denominationcoins, often for the outer cladding. The US 5-cent coin called anickelconsists of 75% copper and 25% nickel and has a homogeneous composition. The alloy consisting of 90% copper and 10% nickel is remarkable for its resistance to corrosion and is used in various parts that are exposed to seawater. Alloys of copper with aluminium (about 7%) have a pleasant golden color and are used in decorations.[16]Some lead-free solders consist of tin alloyed with a small proportion of copper and other metals.[31]Compounds

A sample ofcopper(I) oxide.

See also:Category:Copper compoundsCopper forms a rich variety of compounds, usually withoxidation states+1 and +2, which are often calledcuprousandcupric, respectively.[32]Binary compoundsAs with other elements, the simplest compounds of copper are binary compounds, i.e. those containing only two elements. The principal ones are the oxides, sulfides, andhalides. Bothcuprousandcupric oxidesare known. Among the numerouscopper sulfides, important examples includecopper(I) sulfideandcopper(II) sulfide.

The cuprous halides withchlorine,bromine, andiodineare known, as are the cupric halides withfluorine,chlorine, andbromine. Attempts to prepare copper(II) iodide give cuprous iodide and iodine.[32]2 Cu2++ 4 I 2 CuI + I2Coordination chemistry

Copper(II) gives a deep blue coloration in the presence of ammonia ligands. The one used here istetramminecopper(II) sulfate.

Copper, like all metals, formscoordination complexeswithligands. In aqueous solution, copper(II) exists as [Cu(H2O)6]2+. This complex exhibits the fastest water exchange rate (speed of water ligands attaching and detaching) for any transitionmetal aquo complex. Adding aqueoussodium hydroxidecauses the precipitation of light blue solidcopper(II) hydroxide. A simplified equation is:

Cu2++ 2 OH Cu(OH)2Aqueous ammoniaresults in the same precipitate. Upon adding excess ammonia, the precipitate dissolves, formingtetraamminecopper(II):

Cu(H2O)4(OH)2+ 4 NH3 [Cu(H2O)2(NH3)4]2++ 2 H2O + 2 OHMany otheroxyanionsform complexes; these includecopper(II) acetate,copper(II) nitrate, andcopper(II) carbonate.Copper(II) sulfateforms a blue crystalline pentahydrate, which is the most familiar copper compound in the laboratory. It is used in afungicidecalled theBordeaux mixture.[33]

Ball-and-stick modelof the complex [Cu(NH3)4(H2O)2]2+, illustrating theoctahedral coordination geometrycommon for copper(II).

Polyols, compounds containing more than one alcoholfunctional group, generally interact with cupric salts. For example, copper salts are used to test forreducing sugars. Specifically, usingBenedict's reagentandFehling's solutionthe presence of the sugar is signaled by a color change from blue Cu(II) to reddish copper(I) oxide.[34]Schweizer's reagent and related complexes withethylenediamineand otheraminesdissolve cellulose.[35]Amino acidsform very stable chelate complexes with copper(II). Many wet-chemical tests for copper ions exist, one involvingpotassium ferrocyanide, which gives a brown precipitate with copper(II) salts.