Copper
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For other uses, seeCopper (disambiguation).
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
view talk editreferences
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.