Editing Copper (section)

==Characteristics==

===Physical===
[[File:Cu-Scheibe.JPG|thumb|left|upright=0.7|A copper disc (99.95% pure) made by [[continuous casting]]; [[industrial etching|etched]] to reveal [[crystallite]]s]]

[[File:Molten copper in bright sunlight.gif|upright=0.7|thumb|left|Copper just above its melting point keeps its pink luster color when enough light outshines the orange [[incandescence]] color.]]

Copper, [[silver]], and [[gold]] are in [[group 11 element|group 11]] of the periodic table; these three metals have one s-orbital electron on top of a filled d-[[electron shell]] and are characterized by high [[ductility]], and electrical and thermal conductivity. The filled d-shells in these elements contribute little to interatomic interactions, which are dominated by the s-electrons through [[metallic bond]]s. Unlike metals with incomplete d-shells, metallic bonds in copper are lacking a [[covalent bond|covalent]] character and are relatively weak. This observation explains the low [[hardness]] and high ductility of [[monocrystalline|single crystals]] of copper.<ref name="b1">{{cite book|first1=George L. |last1=Trigg|first2=Edmund H. |last2=Immergut|title=Encyclopedia of Applied Physics|url=https://books.google.com/books?id=sVQ5RAAACAAJ|access-date=2 May 2011|year=1992|publisher=VCH |isbn=978-3-527-28126-8|pages=267–272|volume=4: Combustion to Diamagnetism}}</ref> 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-grained [[polycrystalline]] form, which has greater strength than monocrystalline forms.<ref>{{cite book|last1 = Smith |first1=William F.|last2 = Hashemi |first2=Javad|name-list-style = amp |title = Foundations of Materials Science and Engineering|page = 223|publisher = McGraw-Hill Professional|date= 2003|isbn = 978-0-07-292194-6}}</ref>

The softness of copper partly explains its high electrical conductivity ({{val|59.6|e=6|u=[[Siemens (unit)|S]]/m}}) and high thermal conductivity, second highest (second only to silver) among pure metals at room temperature.<ref name="CRC">{{cite book|last = Hammond |first=C. R.|title = The Elements, in Handbook of Chemistry and Physics|edition = 81st|publisher = CRC Press|isbn = 978-0-8493-0485-9|date = 2004|url = https://archive.org/details/crchandbookofche81lide}}</ref> This is because the resistivity to electron transport in metals at room temperature originates primarily from scattering of electrons on thermal vibrations of the lattice, which are relatively weak in a soft metal.<ref name="b1" /> The maximum possible current density of copper in open air is approximately {{val|3.1|e=6|u=A/m<sup>2</sup>}}, above which it begins to heat excessively.<ref>{{cite book|author=Resistance Welding Manufacturing Alliance |title=Resistance Welding Manual|date=2003|publisher=Resistance Welding Manufacturing Alliance|isbn=978-0-9624382-0-2|edition=4th|pages=18–12}}</ref>

Copper is one of a few metallic elements with a natural color other than gray or silver.<ref>{{Cite book|last1 = Chambers|first1 = William|last2 = Chambers|first2 = Robert|title = Chambers's Information for the People|publisher = W. & R. Chambers|date = 1884|volume = L|page = 312|edition = 5th|url = https://books.google.com/books?id=eGIMAAAAYAAJ|isbn = 978-0-665-46912-1}}</ref> Pure copper is orange-red and acquires a reddish [[tarnish]] when exposed to air. This is due to the low [[plasma frequency]] of the metal, which lies in the red part of the visible spectrum, causing it to absorb the higher-frequency green and blue colors.<ref>{{cite web |last1=Ramachandran |first1=Harishankar |title=Why is Copper Red? |url=http://ee.iitm.ac.in/~hsr/ec301/copper.pdf |website=[[IIT Madras]] |access-date=27 December 2022 |date=14 March 2007}}</ref>

As with other metals, if copper is put in contact with another metal in the presence of an [[electrolyte]], [[galvanic corrosion]] will occur.<ref>{{cite web|title=Galvanic Corrosion|url=http://www.corrosion-doctors.org/Forms-galvanic/galvanic-corrosion.htm|work=Corrosion Doctors|access-date=29 April 2011}}</ref>

===Chemical===
[[File:Copper wire comparison.JPG|left|upright=0.7|thumb|Unoxidized copper wire (left) and oxidized copper wire (right)]]
[[File:Royal Observatory Edinburgh East Tower 2010 cropped.jpg|thumb|The East Tower of the [[Royal Observatory, Edinburgh]], showing the contrast between the refurbished copper installed in 2010 and the green color of the original 1894 copper]]
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 the [[rust]] that forms on iron in moist air, protects the underlying metal from further corrosion ([[passivation (chemistry)|passivation]]). A green layer of [[verdigris]] (copper carbonate) can often be seen on old copper structures, such as the roofing of many older buildings<ref name="Grieken-2005">{{Cite book|url=https://books.google.com/books?id=3qL3vfUZHMYC|title=Cultural Heritage Conservation and Environmental Impact Assessment by Non-Destructive Testing and Micro-Analysis|last1=Grieken|first1=Rene van|last2=Janssens|first2=Koen|date=2005|publisher=CRC Press|isbn=978-0-203-97078-2|page=197|language=en}}</ref> and the [[Statue of Liberty]].<ref>{{cite web|title=Copper.org: Education: Statue of Liberty: Reclothing the First Lady of Metals – Repair Concerns|url=http://www.copper.org/education/liberty/liberty_reclothed1.html|work=Copper.org|access-date=11 April 2011}}</ref> Copper [[tarnish]]es when exposed to some [[sulfur]] compounds, with which it reacts to form various [[copper sulfide]]s.<ref>{{cite journal|last1=Rickett|first1=B. I.|last2=Payer|first2=J. H.|title=Composition of Copper Tarnish Products Formed in Moist Air with Trace Levels of Pollutant Gas: Hydrogen Sulfide and Sulfur Dioxide/Hydrogen Sulfide|journal=Journal of the Electrochemical Society|date=1995|volume=142|issue=11|pages=3723–3728|doi=10.1149/1.2048404|bibcode=1995JElS..142.3723R}}</ref>

===Isotopes===
{{Main|Isotopes of copper}}
There are 29 [[isotope]]s of copper. {{SimpleNuclide|Copper|63}} and {{SimpleNuclide|Copper|65}} are stable, with {{SimpleNuclide|Copper|63}} comprising approximately 69% of naturally occurring copper; both have a [[Spin (physics)|spin]] of {{frac|3|2}}.<ref name="nubase">{{NUBASE 2003}}</ref> The other isotopes are [[radioactivity|radioactive]], with the most stable being {{SimpleNuclide|Copper|67}} with a [[half-life]] of 61.83&nbsp;hours.<ref name="nubase" /> Seven [[nuclear isomer|metastable isomers]] have been characterized; {{SimpleNuclide|Copper|68m}} is the longest-lived with a half-life of 3.8 minutes. Isotopes with a [[mass number]] above 64 decay by [[beta decay|β<sup>−</sup>]], whereas those with a mass number below 64 decay by [[positron emission|β<sup>+</sup>]]. [[Copper-64|{{SimpleNuclide|Copper|64}}]], which has a half-life of 12.7 hours, decays both ways.<ref>{{cite web |url=http://www.nndc.bnl.gov/chart/reCenter.jsp?z=29&n=35 |title=Interactive Chart of Nuclides |work=National Nuclear Data Center |access-date=8 April 2011 |archive-date=25 August 2013 |archive-url=https://web.archive.org/web/20130825141152/http://www.nndc.bnl.gov/chart/reCenter.jsp?z=29&n=35 |url-status=dead }}</ref>

{{SimpleNuclide|Copper|62}} and {{SimpleNuclide|Copper|64}} have significant applications. {{SimpleNuclide|Copper|62}} is used in {{SimpleNuclide|Copper|62}}Cu-PTSM as a [[radioactive tracer]] for [[positron emission tomography]].<ref>{{Cite journal | last1 = Okazawad | first1 = Hidehiko | last2 = Yonekura | first2 = Yoshiharu | last3 = Fujibayashi | first3 = Yasuhisa | last4 = Nishizawa | first4 = Sadahiko | last5 = Magata | first5 = Yasuhiro | last6 = Ishizu | first6 = Koichi | last7 = Tanaka | first7 = Fumiko | last8 = Tsuchida |first8 = Tatsuro |last9 = Tamaki |first9 = Nagara |last10 = Konishi | first10 = Junji |date=1994 |title=Clinical Application and Quantitative Evaluation of Generator-Produced Copper-62-PTSM as a Brain Perfusion Tracer for PET |journal=Journal of Nuclear Medicine |volume=35 |issue=12 |pages=1910–1915 |url=http://jnm.snmjournals.org/cgi/reprint/35/12/1910.pdf|pmid=7989968 }}</ref>

===Occurrence===
{{See also|List of copper ores}}
[[File:Native Copper from the Keweenaw Peninsula Michigan.jpg|thumb|right|upright=0.7|Native copper from the Keweenaw Peninsula, Michigan, about {{convert|2.5|in|cm}} long]]
Copper is produced in massive stars<ref>{{cite journal|last1=Romano|first1=Donatella|last2=Matteucci|first2=Fransesca|title=Contrasting copper evolution in ω Centauri and the Milky Way|journal=Monthly Notices of the Royal Astronomical Society: Letters|date=2007|volume=378|issue=1|pages=L59–L63|doi=10.1111/j.1745-3933.2007.00320.x|doi-access=free |bibcode=2007MNRAS.378L..59R|arxiv = astro-ph/0703760|s2cid=14595800}}</ref> and is present in the Earth's crust in a proportion of about 50 [[parts per million]] (ppm).<ref name="emsley">{{cite book|author=Emsley, John|title=Nature's building blocks: an A–Z guide to the elements|url=https://archive.org/details/naturesbuildingb0000emsl|url-access=registration|access-date=2 May 2011|year=2003|publisher=Oxford University Press|isbn=978-0-19-850340-8|pages=[https://archive.org/details/naturesbuildingb0000emsl/page/121 121]–125}}</ref> In nature, copper occurs in a variety of minerals, including [[native copper]], copper sulfides such as [[chalcopyrite]], [[bornite]], [[digenite]], [[covellite]], and [[chalcocite]], copper [[sulfosalt minerals|sulfosalts]] such as [[tetrahedrite|tetrahedite-tennantite]], and [[enargite]], copper carbonates such as [[azurite]] and [[malachite]], and as copper(I) or copper(II) oxides such as [[cuprite]] and [[tenorite]], respectively.<ref name="CRC" /> The largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on the [[Keweenaw Peninsula]] in Michigan, US.<ref name="emsley" /> Native copper is a [[polycrystal]], with the largest single crystal ever described measuring {{nowrap|4.4 × 3.2 × 3.2 cm}}.<ref>{{cite journal|url = http://www.minsocam.org/ammin/AM66/AM66_885.pdf|journal = American Mineralogist|volume = 66|page=885|date= 1981|title= The largest crystals|last = Rickwood |first=P. C.}}</ref> Copper is the 26th most abundant element in [[Earth's crust]], representing 50&nbsp;ppm compared with 75&nbsp;ppm for [[zinc]], and 14&nbsp;ppm for [[lead]].<ref>{{cite book|author=Emsley, John|title=Nature's building blocks: an A–Z guide to the elements|url=https://archive.org/details/naturesbuildingb0000emsl|url-access=registration|access-date=2 May 2011|year=2003|publisher=Oxford University Press|isbn=978-0-19-850340-8|pages=124, 231, 449, 503}}</ref>

Typical background concentrations of copper do not exceed {{val|1|u=ng/m3}} in the atmosphere; {{val|150|u=mg/kg}} in soil; {{val|30|u=mg/kg}} in vegetation; 2&nbsp;μg/L in freshwater and {{val|0.5|u=μg/L}} in seawater.<ref>{{Cite book|last=Rieuwerts|first=John|url=https://www.worldcat.org/oclc/886492996|title=The Elements of Environmental Pollution|publisher=Earthscan Routledge|year=2015|isbn=978-0-415-85919-6|location=London and New York|pages=207|oclc=886492996}}</ref>