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{{Infobox carbon}}
'''Carbon''' ({{pronEng|kɑrbən}}) is a [[chemical element]] with [[chemical symbol|symbol]] '''C''' and [[atomic number]] 6. As a member of [[group 14]] on the [[periodic table]], it is [[nonmetal]]lic and [[tetravalence|tetravalent]]&mdash;making four electrons available to form [[covalent bond|covalent]] [[chemical bond]]s. There are three naturally occurring [[isotopes]], with [[Carbon-12|<sup>12</sup>C]] and [[Carbon-13|<sup>13</sup>C]] being stable, while [[Carbon-14|<sup>14</sup>C]] is [[radioactive]], decaying with a [[half-life]] of about 5700 years.<ref name="isotopes">{{cite web|url=http://www.webelements.com/webelements/elements/text/C/isot.html|title=Carbon - Naturally occurring isotopes|publisher=WebElements Periodic Table|accessdate=2008-10-09}}</ref> Carbon is one of the [[Discoveries of the chemical elements|few elements known to man since antiquity]].<ref>{{cite web |url=http://www.chemicalelements.com/show/dateofdiscovery.html |title=Periodic Table: Date of Discovery|publisher=Chemical Elements.com|accessdate=2007-03-13}}</ref><ref name=D2>{{cite web |url=http://chemistry.about.com/library/das/aa030303a.htm |title=Timeline of Element Discovery|accessdate=2007-03-13}}</ref> The name "carbon" comes from [[Latin language]] ''carbo'', [[coal]], and, in some [[Romance languages]], the word carbon can refer both to the element and to coal.

There are several [[allotropes of carbon]] of which the best known are [[graphite]], [[diamond]], and [[amorphous carbon]].<ref name="therm prop">{{cite web |url=http://invsee.asu.edu/nmodules/Carbonmod/point.html |title=World of Carbon| Interactive Nano-visulisation in Science &Engineering Edukation (IN-VSEE)|accessdate=2008-10-09}}</ref> The [[physical properties]] of carbon vary widely with the allotropic form. For example, diamond is highly [[Transparency (optics)|transparent]], while graphite is [[Opacity (optics)|opaque]] and black. Diamond is among the hardest materials known, while graphite is soft enough to form a streak on paper. Diamond has a very low [[electric conductivity]], while graphite is a very good [[Electrical conductor|conductor]]. Under normal conditions, diamond has the highest [[thermal conductivity]] of [[List of thermal conductivities|all known materials]]. All the allotropic forms are solids under [[normal conditions]] but graphite is the most [[Thermodynamic equilibrium|thermodynamically stable]].

All forms of carbon are highly stable, requiring high temperature to react even with oxygen. The most common [[oxidation state]] of carbon in [[inorganic compounds]] is +4, while +2 is found in [[carbon monoxide]] and other [[transition metal]] [[carbonyl]] complexes. The largest sources of inorganic carbon are [[limestone]]s, [[dolomite]]s and [[carbon dioxide]], but significant quantities occur in organic deposits of [[coal]], [[peat]], [[oil]] and [[methane clathrate]]s. Carbon forms more [[chemical compound|compounds]] than any other element, with almost ten million pure [[organic compound]]s described to date, which in turn are a tiny fraction of such compounds that are theoretically possible under standard conditions.<ref name=lanl>{{cite web|author=Chemistry Operations|date=December 15, 2003|url=http://periodic.lanl.gov/elements/6.html|title=Carbon|publisher=Los Alamos National Laboratory|accessdate=2008-10-09}}</ref>

Carbon is the [[Abundance of the chemical elements|fourth most abundant element in the universe by mass]] after [[hydrogen]], [[helium]], and [[oxygen]]. It is present in all known [[life]]forms, and in the human body, carbon is the second most abundant element by mass (about 18.5%) after oxygen.<ref>{{cite web |url=http://www.daviddarling.info/encyclopedia/E/elbio.html|title=Biological Abundance of Elements|publisher = The Internet Enceclypedia of Science |accessdate=2008-10-09}}</ref> This abundance, together with the unique diversity of [[organic compounds]] and their unusual polymer-forming ability at the temperatures commonly encountered on [[Earth]], make this element the chemical basis of all known [[life]].

== Characteristics==
The different forms or ''[[allotropes]]'' of carbon (see below) include the hardest naturally occurring substance, [[diamond]], and also one of the softest known substances, [[graphite]]. Moreover, it has an affinity for [[chemical bond|bonding]] with other small [[atom]]s, including other carbon atoms, and is capable of forming multiple stable [[covalent]] bonds with such atoms. As a result, carbon is known to form nearly ten million different compounds; the large majority of all [[chemical compounds]].<ref name=lanl>{{cite web
| author=Chemistry Operations
| date=December 15, 2003
| url=http://periodic.lanl.gov/elements/6.html
| title=Carbon
| publisher=Los Alamos National Laboratory
| accessdate=2007-11-21
}}</ref> Carbon also has the highest [[melting point|melting]] and [[sublimation (chemistry)|sublimation]] point of all elements. At [[atmospheric pressure]] it has no actual melting point as its [[triple point]] is at 10 MPa (100 [[bar (unit)|bar]]) so it sublimates above 4000 K.<ref name="triple">{{cite journal | journal = Nature | volume = 276 | pages = 695&ndash;696 |year = 1978 | doi = 10.1038/276695a0 | title = The controversial carbon solid−liquid−vapour triple point | first = A. | last = Greenville Whittaker}}</ref> Carbon sublimes in a carbon arc which has a temperature of about 5800K. Thus, irrespective of its allotropic form, carbon remains solid at higher temperatures than the highest melting point metals such as [[tungsten]] or [[rhenium]]. Although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature.

[[Image:Diamond and graphite.jpg|thumb|left|Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in structure.]]

Carbon compounds form the basis of all life on [[Earth]] and the [[carbon-nitrogen cycle]] provides some of the energy produced by the [[Sun]] and other [[star]]s. Although it forms an extraordinary variety of compounds, most forms of carbon are comparatively unreactive under normal conditions. At standard temperature and pressure, it resists all but the strongest oxidizers. It does not react with [[sulfuric acid]], [[hydrochloric acid]], [[chlorine]] or any alkalis. At elevated temperatures carbon reacts with oxygen to form carbon oxides, and will reduce such metal oxides as iron oxide to the metal. This [[exothermic]] reaction is used in the iron and steel industry to control the carbon content of steel:<br>
{{chem|Fe|3|O|4}} + 4C<sub>(s)</sub> → 3Fe<sub>(s)</sub> + 4CO<sub>(g)</sub><br>
with [[sulfur]] to form [[carbon disulfide]] and with steam in the coal-gas reaction<br>
C<sub>(s)</sub> + H<sub>2</sub>O<sub>(g)</sub> → CO<sub>(g)</sub> + H<sub>2(g)</sub>.<br>
Carbon combines with some metals at high temperatures to form metallic carbides, such as the iron carbide [[cementite]] in steel, and [[tungsten carbide]], widely used as an [[abrasive]] and for making hard tips for cutting tools.

[[Graphene]], which occurs naturally in [[graphite]], is the strongest substance known to man, according to a study released in August 2008 by [[Columbia University]]. However, the process of separating it from [[graphite]] will require some technological development before it is economical enough to be used in industrial processes.<ref name="nypost"> {{cite web | url = http://www.nypost.com/seven/08252008/news/regionalnews/toughest_stuff__known_to_man_125993.htm | title = Toughest Stuff Known to Man : Discovery Opens Door to Space Elevator | first = Bill | last = Sanderson | publisher = nypost.com | date = 2008-08-25 | accessdate = 2008-10-09}}</ref>

The system of carbon allotropes spans a range of extremes:
{| class="wikitable"
|style="width: 50%;"| Synthetic [[diamond nanorods]] are the hardest materials known.
| Graphite is one of the softest materials known.
|-
| Diamond is the ultimate [[abrasive]].
| Graphite is a very good [[lubricant]].
|-
| Diamond is an excellent electrical [[insulator]].
| Graphite is a [[Electrical conductor|conductor]] of electricity.
|-
| Diamond is the best known [[List of thermal conductivities|thermal conductor]]
| Some forms of graphite are used for [[thermal insulation]] (i.e. firebreaks and heatshields)
|-
| Diamond is highly transparent.
| Graphite is [[opaque]].
|-
| Diamond crystallizes in the [[cubic (crystal system)|cubic system]].
| Graphite crystallizes in the [[hexagonal (crystal system)|hexagonal system]].
|-
| Amorphous carbon is completely [[isotropic]].
| Carbon nanotubes are among the most [[anisotropic]] materials ever produced.
|}

=== Allotropes ===
{{main|Allotropes of carbon}}
[[Atomic carbon]] is a very short-lived species and therefore, carbon is stabilized in various multi-atomic structures with different molecular configurations called [[allotropes]]. The three relatively well-known allotropes of carbon are [[amorphous carbon]], [[graphite]], and [[diamond]]. Once considered exotic, [[fullerene]]s are nowadays commonly synthesized and used in research; they include [[buckyball]]s,<ref name="buckyballs"/><ref name="nanotubes">{{citebook|editor=Ebbesen, TW |year=1997 |title=Carbon nanotubes—preparation and properties |publisher=CRC Press|location=Boca Raton, Florida}}</ref> [[carbon nanotube]]s,<ref name="nanotubes2">{{cite journal |editor=MS Dresselhaus, G Dresselhaus, Ph Avouris |year=2001 |title=Carbon nanotubes: synthesis, structures, properties and applications |journal=Topics in Applied Physics |volume=80 |co-authors= Springer, Heidelberg| isbn = 3540410864}}</ref> [[carbon nanobud]]s<ref name="nanobuds">{{cite journal |co-authors=Nasibulin AG, Pikhitsa PV, Jiang H, et al. |year=2007 |title=A novel hybrid carbon material |journal=Nature Nanotechnology |volume=2 |pages=156&ndash;161 |doi=10.1038/nnano.2007.37 |author=Nasibulin, Albert G.}}</ref> and [[carbon nanofibers|nanofibers]].<ref>{{cite journal |co-authors=Nasibulin AG, Anisimov AS, Pikhitsa PV, et al. |year=2007 |title=Investigations of NanoBud formation |journal=Chemical Physics Letters |volume=446 |pages=109&ndash;114 |doi=10.1016/j.cplett.2007.08.050 |author=Nasibulin, A}}</ref><ref>{{cite journal |co-authors=R Vieiraa, M-J Ledouxa and C Pham-Huu |year=2004 |title=Synthesis and characterisation of carbon nanofibres with macroscopic shaping formed by catalytic decomposition of C<sub>2</sub>H<sub>6</sub>/H<sub>2</sub> over nickel catalyst |journal=Applied Catalysis A |volume=274 |pages=1&ndash;8 |doi=10.1016/j.apcata.2004.04.008 |author=Vieira, R}}</ref> Several other exotic allotropes have also been discovered, such as [[aggregated diamond nanorods]],<ref>{{cite web |url=http://physicsweb.org/articles/news/9/8/16/1?rss=2.0 |title=Diamonds are not forever |publisher=physicsweb.org |accessdate=2007-12-21}}</ref> [[lonsdaleite]],<ref name="lonsdaletite">{{cite journal |co-authors=Frondel, C and Marvin UB |year=1967 |title=Lonsdaleite, a new hexagonal polymorph of diamond |journal=Nature |volume=214 |pages=587&ndash;589 |doi=10.1038/214587a0 |first = Frondel | last = Clifford}}</ref> [[glassy carbon]],<ref name="glassy carbon"/> [[carbon nanofoam]]<ref>{{cite journal |co-authors=Rode AV, Hyde ST, Gamaly EG, et al. |year=1999 |title=Structural analysis of a carbon foam formed by high pulse-rate laser ablation |journal=Applied Physics A-Materials Science & Processing |volume=69 |pages=S755&ndash;S758 |doi=10.1007/s003390051522 |author=Rode, A.V.}}</ref> and [[linear acetylenic carbon]].<ref name=LAC>Carbyne and Carbynoid Structures Series: Physics and Chemistry of Materials with Low-Dimensional Structures, Vol. 21 Heimann, R.B.; Evsyukov, S.E.; Kavan, L. (Eds.) 1999, 452 p., Hardcover ISBN 0-7923-5323-4</ref>

*The [[amorphous]] form, is an assortment of carbon atoms in a non-crystalline, irregular, glassy state, which is essentially [[graphite]] but not held in a crystalline macrostructure. It is present as a powder, and is the main constituent of substances such as [[charcoal]], [[lampblack]] ([[soot]]) and [[activated carbon]].

*At normal pressures carbon takes the form of [[graphite]], in which each atom is bonded trigonally to three others in a plane composed of fused [[hexagon]]al rings, just like those in [[aromatic hydrocarbon]]s. The resulting network is 2-dimensional, and the resulting flat sheets are stacked and loosely bonded through weak [[Van der Waals force]]s. This gives graphite its softness and its [[cleaving]] properties (the sheets slip easily past one another). Because of the delocalization of one of the outer electrons of each atom to form a [[Delocalized electron|π-cloud]], graphite conducts [[electricity]], but only in the plane of each [[covalent bond|covalently bonded]] sheet. This results in a lower bulk [[electrical conductivity]] for carbon than for most [[metals]]. The delocalization also accounts for the energetic stability of graphite over diamond at room temperature.

[[Image:Eight Allotropes of Carbon.png|thumb|350px|right|Some allotropes of carbon: a) [[diamond]]; b) [[graphite]]; c) [[lonsdaleite]]; d–f) [[fullerene]]s (C60, C540, C70); g) [[amorphous carbon]]; h) [[carbon nanotube]].]]

*At very high pressures carbon forms the more compact allotrope [[diamond]], having nearly twice the density of graphite. Here, each atom is bonded [[tetrahedron|tetrahedrally]] to four others, thus making a 3-dimensional network of puckered six-membered rings of atoms. Diamond has the same [[cubic crystal system|cubic structure]] as [[silicon]] and [[germanium]] and, thanks to the strength of the carbon-carbon [[chemical bond|bonds]] is the hardest naturally occurring substance [[Mohs scale|in terms of resistance to scratching]]. Contrary to the popular belief that ''"[[diamonds are forever]]"'', they are in fact thermodynamically unstable under normal conditions and transform into [[graphite]].<ref name="therm prop"/> But due to a high activation energy barrier, the transition into graphite is so extremely slow at room temperature as to be unnoticeable.

*Under some conditions, carbon crystallizes as [[lonsdaleite]]. This form is similar to diamond but has a [[hexagonal]] [[crystal]] lattice.<ref name="lonsdaletite"/>
*[[Fullerene]]s have a graphite-like structure, but instead of purely [[hexagonal crystal system|hexagonal]] packing, they also contain pentagons (or even heptagons) of carbon atoms, which bend the sheet into spheres, ellipses or cylinders. The properties of fullerenes (split into [[buckyball]]s, [[carbon nanotube|buckytube]]s and [[nanobud]]s) have not yet been fully analyzed and represents an intense area of research in [[nanomaterials]]. The name ''"fullerene"'' is given after [[Buckminster Fuller|Richard Buckminster Fuller]], developer of some [[geodesic dome]]s,{{Fact|date=November 2007}} which resemble the structure of fullerenes. The buckyballs are fairly large molecules formed completely of carbon bonded trigonally, forming [[spheroid]]s (the best-known and simplest is the soccerball-shaped structure C<sub>60</sub> [[buckminsterfullerene]]).<ref name="buckyballs"/> Carbon nanotubes are structurally similar to buckyballs, except that each atom is bonded trigonally in a curved sheet that forms a hollow [[cylinder (geometry)|cylinder]].<ref name="nanotubes"/><ref name="nanotubes2"/> Nanobuds were first published in 2007 and are hybrid bucky tube/buckyball materials (buckyballs are covalently bonded to the outer wall of a nanotube) that combine the properties of both in a single structure.<ref name="nanobuds"/>

*Of the other discovered allotropes, [[aggregated diamond nanorods]] were synthesised in 2005 and are believed to be the hardest substance known yet.<ref>{{cite web |url=http://www.esrf.eu/NewsAndEvents/Spotlight/spotlight25nanorods/ |title=Aggregated Diamond Nanorods, the Densest and Least Compressible Form of Carbon |accessdate=2007-12-21}}</ref> [[Carbon nanofoam]] is a [[ferromagnetic]] allotrope discovered in 1997. It consists of a low-density cluster-assembly of carbon atoms strung together in a loose three-dimensional web, in which the atoms are bonded trigonally in six- and seven-membered rings. It is among the lightest known solids, with a density of about 2 kg/m³.<ref>{{cite web |url=http://newton.ex.ac.uk/aip/physnews.678.html#1 |title=Carbon Nanofoam is the World's First Pure Carbon Magnet |accessdate=2007-12-21}}</ref> Similarly, [[glassy carbon]] contains a high proportion of closed [[porosity]].<ref name="glassy carbon"/> But unlike normal graphite, the graphitic layers are not stacked like pages in a book, but have a more random arrangement. [[Linear acetylenic carbon]]<ref name=LAC>Carbyne and Carbynoid Structures Series: Physics and Chemistry of Materials with Low-Dimensional Structures, Vol. 21 Heimann, R.B.; Evsyukov, S.E.; Kavan, L. (Eds.) 1999, 452 p., Hardcover ISBN 0-7923-5323-4</ref> has the chemical structure<ref>Carbyne and Carbynoid Structures Series: Physics and Chemistry of Materials with Low-Dimensional Structures, Vol. 21 Heimann, R.B.; Evsyukov, S.E.; Kavan, L. (Eds.) 1999, 452 p., Hardcover ISBN 0-7923-5323-4</ref> -(C:::C)<sub>n</sub>- .Carbon in this modification is linear with ''sp'' [[orbital hybridisation]], and is a [[polymer]] with alternating single and triple bonds. This type of carbyne is of considerable interest to [[nanotechnology]] as its Young's modulus is forty times that of the hardest known material - diamond.<ref>Harder than Diamond: Determining the Cross-Sectional Area and Young's Modulus of Molecular Rods, Lior Itzhaki et al, Angew. Chem. Int. Ed. 2005, 44, 7432&ndash;7435.</ref>

<!-- [[Carbon fiber]]s are similar to graphite.{{Fact|date=November 2007}} Under special treatment (stretching of organic fibers and carbonization) it is possible to arrange the carbon planes in direction of the fiber.{{Fact|date=November 2007}} Perpendicular to the fiber axis there is no orientation of the carbon planes. The result are fibers with a higher [[specific strength]] than steel.{{Fact|date=November 2007}} -->

=== Occurrence ===
[[Image:GraphiteOreUSGOV.jpg|thumb|200px|left|Graphite ore]]
[[Image:Rough diamond.jpg|left|thumb|200px|Raw diamond crystal.]]

Carbon is the [[Abundance of the chemical elements|fourth most abundant chemical element]] in the universe by mass after hydrogen, helium, and oxygen. Carbon is abundant in the [[Sun]], [[star]]s, [[comet]]s, and in the [[celestial body's atmosphere|atmospheres]] of most [[planet]]s. Some [[meteorite]]s contain microscopic diamonds that were formed when the [[solar system]] was still a [[protoplanetary disk]]. Microscopic diamonds may also be formed by the intense pressure and high temperature at the sites of meteorite impacts.<ref>{{cite book |author=Mark |last=Mark |year=1987 |title=Meteorite Craters |publisher=University of Arizona Press}}</ref>

[[Image:TIC oceans.png|thumb|right|200px|"Present day" (1990s) sea surface [[Total inorganic carbon|dissolved inorganic carbon]] concentration (from the [[Global Ocean Data Analysis Project|GLODAP]] [[climatology]])]]

In combination with [[oxygen]] in [[carbon dioxide]], carbon is found in the Earth's atmosphere (in quantities of approximately 810 [[gigatonne]]s) and dissolved in all water bodies (approximately 36000 gigatonnes). Around 1900 gigatonnes are present in the [[biosphere]]. [[Hydrocarbons]] (such as [[coal]], [[petroleum]], and [[natural gas]]) contain carbon as well &mdash; [[coal]] "reserves" (not "resources") amount to around 900 gigatonnes, and [[oil reserves]] around 150 gigatonnes. With smaller amounts of [[calcium]], [[magnesium]], and [[iron]], carbon is a major component of very large masses [[carbonate]] [[Rock (geology)|rock]] ([[limestone]], [[dolomite]], [[marble]] etc.).

[[Coal]] is a significant commercial source of mineral carbon; [[anthracite]] containing 92-98% carbon{{Fact|date=November 2007}} and the largest source (4000 Gt, or 80% of coal, gas and oil reserves) of carbon in a form suitable for use as fuel.<ref>{{cite journal |first = James | last = Kasting |year=1998 |title=The Carbon Cycle, Climate, and the Long-Term Effects of Fossil Fuel Burning |journal=Consequences: The Nature and Implication of Environmental Change | volume = 4 |number = 1 | url = http://gcrio.org/CONSEQUENCES/vol4no1/carbcycle.html}}</ref>

Graphite is found in large quantities in [[New York]] and [[Texas]], the [[United States]], [[Russia]], [[Mexico]], [[Greenland]], and [[India]].

Natural diamonds occur in the rock [[kimberlite]], found in ancient [[volcano|volcanic]] "necks," or "pipes". Most diamond deposits are in [[Africa]], notably in [[South Africa]], [[Namibia]], [[Botswana]], the [[Republic of the Congo]], and [[Sierra Leone]]. There are also deposits in [[Arkansas]], [[Canada]], the Russian [[Arctic]], [[Brazil]] and in Northern and Western [[Australia]].

Diamonds are now also being recovered from the ocean floor off the [[Cape of Good Hope]]. However, though diamonds are found naturally, about 30% of all industrial diamonds used in the U.S. are now made synthetically.

According to studies from the Massachusetts Institute of Technology, an estimate of the global carbon budget is:{{Fact|date=February 2007}}

{| class="wikitable" style="font-size: 90%; float: right; margin-left: 1em;"
|-
! colspan="2" style="text-align: center;" |Biosphere, oceans, atmosphere
|-
| colspan="2" style="text-align: center;" |0.45 x 10<sup>18</sup> [[kilogram]]s (3.7 x 10<sup>18</sup> [[mole (unit)|moles]])
|-
! colspan="2" style="text-align: center;" |Crust
|-
! Organic carbon
|13.2 x 10<sup>18</sup> kg
|-
!Carbonates
|62.4 x 10<sup>18</sup> kg
|-
! colspan="2" style="text-align: center;" |Mantle
|-
| colspan="2" style="text-align: center;" |1200 x 10<sup>18</sup> kg
|}

Carbon-14 is formed in upper layers of the troposphere and the stratosphere, at altitudes of 9&ndash;15 km, by a reaction that is precipitated by [[cosmic ray]]s. [[Thermal neutron]]s are produced that collide with the nuclei of nitrogen-14, forming carbon-14 and a proton.

=== Isotopes ===
{{main|Isotopes of carbon}}
[[Isotopes]] of carbon are [[atomic nucleus|atomic nuclei]] that contain six [[proton]]s plus a number of [[neutron]]s (varying from 2 to 16). Carbon has two stable, naturally occurring [[isotope]]s.<ref name="isotopes">{{cite web|url=http://www.webelements.com/webelements/elements/text/C/isot.html|title=Carbon - Naturally occurring isotopes|publisher=WebElements Periodic Table|accessdate=2007-12-08}}</ref> The isotope [[carbon-12]] (<sup>12</sup>C) forms 98.93% of the carbon on Earth, while [[carbon-13]] (<sup>13</sup>C) forms the remaining 1.07%.<ref name="isotopes"/> The concentration of <sup>12</sup>C is further increased in biological materials because biochemical reactions discriminate against <sup>13</sup>C.<ref>{{cite journal|last =Gannes|first =Leonard Z.|coauthors =Martínez del Rio, Carlos; Koch, Paul|title =Natural Abundance Variations in Stable Isotopes and their Potential Uses in Animal Physiological Ecology|journal =Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology|volume =119|issue =3|pages =725&ndash;737|publisher =Elsevier Science|location =New York|month= March | year= 1998|url =|doi =10.1016/S1095-6433(98)01016-2|accessdate = }}</ref> In 1961 the [[International Union of Pure and Applied Chemistry]] (IUPAC) adopted the isotope [[carbon-12]] as the basis for [[atomic weight]]s.<ref>{{cite web |url=http://www.bipm.org/en/si/base_units/ |title=Official SI Unit definitions |accessdate=2007-12-21}}</ref> Identification of carbon in [[NMR]] experiments is done with the isotope <sup>13</sup>C.

[[Carbon-14]] (<sup>14</sup>C) is a naturally occurring [[radioisotope]] which occurs in trace amounts on Earth of up to 1 part per [[trillion]] (0.0000000001%), mostly confined to the atmosphere and superficial deposits, particularly of [[peat]] and other organic materials.<ref>{{cite web|last=Brown | first=Tom | date=March 1, 2006|url=http://www.llnl.gov/str/March06/Brown.html|title=Carbon Goes Full Circle in the Amazon|publisher=Lawrence Livermore National Laboratory|accessdate=2007-11-25}}</ref> This isotope decays by 0.158 MeV [[beta decay|β<sup>-</sup> emission]]. Because of its relatively short [[half-life]] of 5730 years, <sup>14</sup>C is virtually absent in ancient rocks, but is created in the [[upper atmosphere]] (lower [[stratosphere]] and upper [[troposphere]]) by interaction of [[nitrogen]] with [[cosmic ray]]s.<ref>{{cite book |author=Bowman, S. |first=S. |last=Bowman |year=1990 |title=Interpreting the past: Radiocarbon dating |publisher=British Museum Press |isbn=0-7141-2047-2}}</ref> The abundance of <sup>14</sup>C in the [[atmosphere]] and in living organisms is almost constant, but decreases predictably in their bodies after death. This principle is used in [[radiocarbon dating]], invented in 1949, which has been used extensively to determine the age of carbonaceous materials with ages up to about 40,000 years.<ref>{{cite book |author=Libby WF |last=Libby |first=WF |year=1952 |title=Radiocarbon dating |publisher=Chicago University Press and references therein}}</ref><ref>{{cite web
|last=Westgren | first=A. | year=1960
|url=http://nobelprize.org/nobel_prizes/chemistry/laureates/1960/press.html
|title=The Nobel Prize in Chemistry 1960
|publisher=Nobel Foundation | accessdate=2007-11-25 }}</ref>

There are 15 known isotopes of carbon and the shortest-lived of these is <sup>8</sup>C which decays through [[proton emission]] and [[alpha decay]] and has a half-life of 1.98739x10<sup>-21</sup> [[Second|s]].<ref>{{cite web |url=http://barwinski.net/isotopes/query_select.php |title=Use query for carbon-8 |accessdate=2007-12-21}}</ref> The exotic <sup>19</sup>C exhibits a [[nuclear halo]], which means its [[radius]] is appreciably larger than would be expected if the [[Atomic nucleus|nucleus]] was a [[sphere]] of constant [[density]].<ref>{{cite web |url=http://www.sciencemag.org/cgi/content/full/286/5437/28?ck=nck |title=Beaming Into the Dark Corners of the Nuclear Kitchen |accessdate=2007-12-21}}</ref>

=== Formation in stars ===
{{main|Triple-alpha process|CNO cycle}}
Formation of the carbon atomic nucleus requires a nearly simultaneous triple collision of [[alpha particle]]s ([[helium]] nuclei) within the core of a [[giant star|giant]] or [[supergiant]] star. This happens in conditions of temperature and helium concentration that the rapid expansion and cooling of the early universe prohibited, and therefore no significant carbon was created during the [[Big Bang]]. Instead, the interiors of stars in the [[H-R diagram|horizontal branch]] transform three helium nuclei into carbon by means of this [[triple-alpha process]]. In order to be available for formation of life as we know it, this carbon must then later be scattered into space as dust, in [[supernovae|supernova]] explosions, as part of the material which later forms second, third-generation star systems which have planets accreted from such dust. The [[Solar System]] is one such [[Metallicity|third-generation star]] system.

One of the fusion mechanisms powering stars is the [[carbon-nitrogen cycle]].

Rotational transitions of various isotopic forms of carbon monoxide (e.g. <sup>12</sup>CO, <sup>13</sup>CO, and C<sup>18</sup>O) are detectable in the [[submillimetre astronomy|submillimeter]] regime, and are used in the study of [[Star formation|newly forming stars]] in [[molecular clouds]].

=== Carbon cycle ===
{{main|Carbon cycle}}
[[Image:Carbon cycle-cute diagram.jpeg|thumb|300px||Diagram of the carbon cycle. The black numbers indicate how much carbon is stored in various reservoirs, in billions of tons ("GtC" stands for gigatons of carbon; figures are circa 2004). The purple numbers indicate how much carbon moves between reservoirs each year. The sediments, as defined in this diagram, do not include the ~70 million GtC of carbonate rock and kerogen.]]
Under terrestrial conditions, conversion of one element to another is very rare. Therefore, the amount of carbon on Earth is effectively constant. Thus, processes that use carbon must obtain it somewhere and dispose of it somewhere else. The paths that carbon follows in the environment make up the [[carbon cycle]]. For example, plants draw [[carbon dioxide]] out of their environment and use it to build biomass, as in [[carbon respiration]] or the [[Calvin cycle]], a process of [[carbon fixation]]. Some of this biomass is eaten by animals, whereas some carbon is exhaled by animals as carbon dioxide. The carbon cycle is considerably more complicated than this short loop; for example, some carbon dioxide is dissolved in the oceans; dead plant or animal matter may become [[petroleum]] or [[coal]], which can burn with the release of carbon, should bacteria not consume it.<ref>{{ cite journal | journal = Science | year = 2000 | volume = 290 | issue = 5490 | pages = 291&ndash;296 | doi = 10.1126/science.290.5490.291 | title = The Global Carbon Cycle: A Test of Our Knowledge of Earth as a System | author = P. Falkowski, R. J. Scholes, E. Boyle, J. Canadell, D. Canfield, J. Elser, N. Gruber, K. Hibbard, P. Högberg, S. Linder, F. T. Mackenzie, B. Moore III, T. Pedersen, Y. Rosenthal, S. Seitzinger, V. Smetacek, W. Steffen.}}</ref><!--10.1007/BF01104986-->

== Compounds ==
=== Inorganic compounds ===
{{main|Compounds of carbon}}

Commonly carbon-containing compounds which are associated with minerals or which do not contain hydrogen or fluorine, are treated separately from classical [[organic compounds]]; however the definition is not rigid (see reference articles above). Among these are the simple oxides of carbon. The most prominent oxide is [[carbon dioxide]] ({{chem|C||O|2}}). This was once the principal constituent of the [[paleoatmosphere]], but is a minor component of the [[Earth's atmosphere]] today.<ref>{{citejournal|author=JS Levine, TR Augustsson and M Natarajan |year=1982 |title=The prebiological paleoatmosphere: stability and composition |journal=Origins of Life and Evolution of Biospheres |volume= 12 |number=3 |pages=245–259 |doi=10.1007/BF00926894}}</ref> Dissolved in [[water (molecule)|water]], it forms [[carbonic acid]] ({{chem|H|2|C||O|3}}), but as most compounds with multiple single-bonded oxygens on a single carbon it is unstable.{{Fact|date=November 2007}} Through this intermediate, though, resonance-stabilized [[carbonate]] [[ion]]s are produced. Some important minerals are carbonates, notably [[calcite]]. [[Carbon disulfide]] ({{chem|C||S|2}}) is similar.

The other common oxide is [[carbon monoxide]] (CO). It is formed by incomplete combustion, and is a colorless, odorless gas. The molecules each contain a triple bond and are fairly [[polar molecule|polar]], resulting in a tendency to bind permanently to hemoglobin molecules, displacing oxygen, which has a lower binding affinity.<ref>{{cite journal |author=Haldane J. |year=1895 |title=The action of carbonic oxide on man |journal=Journal of Physiology |volume=18 |pages=430–462}}</ref><ref>{{cite journal |co-authors=Gorman D, Drewry A, Huang YL & Sames C |year=2003 |title=The clinical toxicology of carbon monoxide |journal=Toxicology |number=187 |pages=25–38 |doi=10.1016/S0300-483X(03)00005-2 |author=Gorman, D |volume=187}}</ref> [[Cyanide]] (CN<sup>–</sup>), has a similar structure, but behaves much like a [[halide]] ion ([[pseudohalogen]]). For example it can form the nitride [[cyanogen]] molecule ((CN)<sub>2</sub>), similar to diatomic halides. Other uncommon oxides are [[carbon suboxide]] ({{chem|C|3|O|2}}),<ref>{{citeweb|title= Compounds of carbon: carbon suboxide|url=http://www.webelements.com/webelements/compounds/text/C/C3O2-504643.html|accessdate=2007-12-03}}</ref> the unstable [[dicarbon monoxide]] (C<sub>2</sub>O),<ref>{{citejournal|author= Bayes K.|title=Photolysis of Carbon Suboxide|journal=[[Journal of the American Chemical Society]]|volume=83|year=1961|pages=3712–3713|doi=10.1021/ja01478a033}}</ref><ref>{{citejournal|author=Anderson D. J.|coauthor=Rosenfeld R. N.|title=Photodissociation of Carbon Suboxide|journal=[[Journal of Chemical Physics]]|volume=94|year=1991|pages=7852–7867|doi=10.1063/1.460121}}</ref> and even [[carbon trioxide]] (CO<sub>3</sub>).<ref>{{citejournal|title=A theoretical study of the structure and properties of carbon trioxide|author=Sabin, J. R.|coauthor=Kim, H.|journal=[[Chemical Physics Letters]]|volume=11|issue=5|pages=593–597|date=11/1971|doi=10.1016/0009-2614(71)87010-0}}</ref><ref>{{citejournal|title=Carbon Trioxide: Its Production, Infrared Spectrum, and Structure Studied in a Matrix of Solid CO<sub>2</sub>|journal=The [[Journal of Chemical Physics]]|year=1966|volume=45|issue=12|pages=4469–4481|doi=10.1063/1.1727526|author=Moll N. G., Clutter D. R., Thompson W. E.}}</ref>

With reactive [[metal]]s, such as [[tungsten]], carbon forms either carbides (C<sup>4–</sup>), or acetylides (C<sub>2</sub><sup>2–</sup>) to form alloys with high melting points. These anions are also associated with [[methane]] and [[acetylene]], both very weak [[acid]]s. With an electronegativity of 2.5,<ref>{{cite book |author= L. Pauling |title= The Nature of the Chemical Bond |edition= 3<sup>rd</sup> ed. |publisher= Cornell University Press |location= Ithaca, NY |year= 1960 |pages= 93 }}</ref> carbon prefers to form [[covalent bond]]s. A few carbides are covalent lattices, like [[carborundum]] (SiC), which resembles [[diamond]].

=== Organic compounds ===
{{main|Organic compound}}
[[Image:Methane-2D-stereo.svg|thumb|right|200px|Structural formula of [[methane]], the simplest possible organic compound]]
Carbon has the ability to form very long chains interconnecting C-C bonds. This property is called [[catenation]]. Carbon-carbon bonds are strong, and stable.{{Fact|date=November 2007}} This property allows carbon to form an almost infinite number of compounds; in fact, there are more known carbon-containing compounds than all the compounds of the other chemical elements combined except those of hydrogen (because almost all organic compounds contain hydrogen too).

The simplest form of an organic molecule is the [[hydrocarbon]]&mdash;a large family of [[organic molecule]]s that are composed of [[hydrogen]] atoms bonded to a chain of carbon atoms. Chain length, side chains and [[functional group]]s all affect the properties of organic molecules. By [[IUPAC]]'s definition, all the other organic compounds are functionalized compounds of hydrocarbons.{{Fact|date=December 2007}}

[[Image:Plastic household items.jpg|thumb|200px|left|Carbon is the basis for all plastic materials that are used in common household items.]]

Carbon occurs in all [[organic material|organic]] [[life]] and is the basis of [[organic chemistry]]. When united with [[hydrogen]], it forms various flammable compounds called [[hydrocarbon]]s which are important to industry as chemical feedstock for the manufacture of [[plastic]]s and [[petrochemicals]] and as [[fossil fuel]]s.

When combined with oxygen and hydrogen, carbon can form many groups of important biological compounds including [[sugar]]s,[[lignan]]s, [[chitin]]s, [[alcohol]]s, [[fat]]s, and aromatic [[ester]]s, [[carotenoids]] and [[terpenes]]. With [[nitrogen]] it forms [[alkaloid]]s, and with the addition of sulfur also it forms [[antibiotic]]s, [[amino acid]]s, and [[rubber]] products. With the addition of phosphorus to these other elements, it forms [[DNA]] and [[RNA]], the chemical-code carriers of life, and [[adenosine triphosphate]] (ATP), the most important energy-transfer molecule in all living cells.

{{clear}}

== History and etymology ==
{{Expand-section|date=January 2008}}
The [[English language|English]] name ''carbon'' comes from the [[Latin]] ''carbo'' for coal and charcoal,<ref>Shorter Oxford English Dictionary, Oxford University Press</ref> and hence comes [[French language|French]] ''charbon'', meaning charcoal. In [[German language|German]], [[Dutch language|Dutch]] and [[Danish language|Danish]], the names for carbon are ''Kohlenstoff'', ''koolstof'' and ''kulstof'' respectively, all literally meaning [[coal]]-substance.

[[Image:Carl Wilhelm Scheele from Familj-Journalen1874.png|thumb|100px|left|Carl Wilhelm Scheele]]
[[Image:Antoine lavoisier.jpg|thumb|100px|left|Antoine Lavoisier in his youth]]
Carbon was discovered in prehistory and was known in the forms of [[soot]] and [[charcoal]] to the earliest [[human]] [[civilization]]s. Diamonds were known probably as early as 2500 BCE in China, while carbon in the forms of [[charcoal]] was made around Roman times by the same chemistry as it is today, by heating wood in a [[pyramid]] covered with [[clay]] to exclude air.<ref name=ancient_China>{{cite news | url = http://news.bbc.co.uk/2/hi/science/nature/4555235.stm | title = Chinese made first use of diamond | publisher = BBC News | date= 17 May 2005 | accessdate = 2007-03-21}}</ref><ref>{{cite web |url=http://www.vanderkrogt.net/elements/elem/c.html |title=Carbonium/Carbon at Elementymology & Elements Multidict |author= Peter van der Krogt |last=van der Krogt |first=Peter |accessdate=2007-12-21}}</ref>

In 1722, [[René Antoine Ferchault de Réaumur|René A. F. de Réaumur]] demonstrated that iron was transformed into steel through the absorption of some substance, now known to be carbon.<ref>{{cite book |author=R-A Ferchault de Réaumur |last=Ferchault de Réaumur |first=R-A |year=1722 |title=L'art de convertir le fer forgé en acier, et l'art d'adoucir le fer fondu, ou de faire des ouvrages de fer fondu aussi finis que le fer forgé (English translation from 1956) |location=Paris, Chicago}}</ref> In 1772, [[Antoine Lavoisier]] showed that diamonds are a form of carbon, when he burned samples of carbon and diamond then showed that neither produced any water and that both released the same amount of [[carbon dioxide]] per [[gram]].
[[Carl Wilhelm Scheele]] showed that graphite, which had been thought of as a form of [[lead]], was instead a type of carbon.<ref>{{citeweb|author=Senese, Fred|url=http://antoine.frostburg.edu/chem/senese/101/inorganic/faq/discovery-of-carbon.shtml | title=Who discovered carbon? | publisher=Frostburg State University |accessdate=2007-11-24}}</ref> In 1786, the French scientists [[Claude Louis Berthollet]], [[Gaspard Monge]] and C. A. Vandermonde then showed that this substance was carbon.<ref>{{citebook|author=Federico Giolitti|year=1914
|title=The Cementation of Iron and Steel|publisher=McGraw-Hill Book Company, inc.}}</ref> In their publication they proposed the name carbone (Latin carbonum) for this element. Antoine Lavoisier listed carbon as an [[chemical element|element]] in his 1789 textbook.<ref>{{citeweb|author=Senese,Fred | date = 200-09-09 | url = http://antoine.frostburg.edu/chem/senese/101/inorganic/faq/discovery-of-carbon.shtml|title=Who discovered carbon?|publisher=Frostburg State University|accessdate=2007-11-24 }}</ref>

A new [[allotrope]] of carbon, [[fullerene]], that was discovered in 1985<ref>{{citejournal|journal=Nature|volume=318|pages=162–163|year=1985|doi=10.1038/318162a0|title=C<sup>60</sup>: Buckminsterfullerene|author=H. W. Kroto, J. R. Heath, S. C. O'Brien, R. F. Curl and R. E. Smalley}}</ref> includes [[nanostructure]]d forms such as [[buckyballs]] and [[nanotubes]].<ref name="buckyballs">{{citeweb|url=http://www.ch.ic.ac.uk/local/projects/unwin/Fullerenes.html|title=Fullerenes(An Overview)|author=Peter Unwin|accessdate=2007-12-08}}</ref> Their discoverers (Curl, Kroto, and Smalley) received the [[Nobel Prize]] in Chemistry in 1996.<ref>{{cite web |url=http://nobelprize.org/nobel_prizes/chemistry/laureates/1996/index.html |title=The Nobel Prize in Chemistry 1996 "for their discovery of fullerenes" |accessdate=2007-12-21}}</ref> The resulting renewed interest in new forms, lead to the discovery of further exotic allotropes, including [[glassy carbon]], and the realization that "[[amorphous carbon]]" is not strictly [[amorphous]].<ref name="glassy carbon">{{cite journal |author=PJF Harris |last=Harris |first=PJF |year=2004 |title=Fullerene-related structure of commercial glassy carbons |journal=Philosophical Magazine, 84, 3159–3167 |doi=10.1007/s10562-007-9125-6 |volume=116 |pages=122}}</ref>

== Production ==
{{Expand-section|date=December 2007}}
===Graphite===
{{main|Graphite}}
Commercially viable natural deposits of graphite occur in many parts of the world, but the most important sources economically are in [[China]], [[India]], [[Brazil]], and [[North Korea]].<ref>[http://minerals.usgs.gov/minerals/pubs/commodity/graphite/myb1-2006-graph.pdf USGS Minerals Yearbook: Graphite, 2006]</ref> Graphite deposits are of [[Metamorphic rock|metamorphic]] origin, found in association with [[quartz]], [[mica]] and [[feldspar]]s in schists, [[gneiss]]es and metamorphosed [[sandstone]]s and [[limestone]] as [[lens (geology)|lenses]] or [[vein (geology)|veins]], sometimes of a [[metre]] or more in thickness. Deposits of graphite in [[Borrowdale]], [[Cumberland]], [[England]] were at first of sufficient size and purity that, until the 1800s, [[pencil]]s were made simply by sawing blocks of natural graphite into strips before encasing the strips in wood. Today, smaller deposits of graphite are obtained by crushing the parent rock and floating the lighter graphite out on water.

According to the [[USGS]], world production of natural graphite in 2006 was 1.03 million tonnes and in 2005 was 1.04 million tonnes (revised), of which the following major exporters produced: China produced 720,000 tonnes in both 2006 and 2005, Brazil 75,600 tonnes in 2006 and 75,515 tonnes in 2005 (revised), Canada 28,000 tonnes in both years, and Mexico (amorphous) 12,500 tonnes in 2006 and 12,357 tonnes in 2005 (revised). In addition, there are two specialist producers: Sri Lanka produced 3,200 tonnes in 2006 and 3,000 tonnes in 2005 of lump or vein graphite, and Madagascar produced 15,000 tonnes in both years, a large portion of it "crucible grade" or very large flake graphite. Some other producers produce very small amounts of "crucible grade".

According to the [[USGS]], U.S. (synthetic) graphite electrode production in 2006 was 132,000 tonnes valued at $495 million and in 2005 was 146,000 tonnes valued at $391 million, and high-modulus graphite (carbon) fiber production in 2006 was 8,160 tonnes valued at $172 million and in 2005 was 7,020 tonnes valued at $134 million.
{{-}}

===Diamond===
{{main|Diamond}}
[[Image:Diamond output2.PNG|thumb|right|Diamond output in 2005]]

The diamond supply chain is controlled by a limited number of powerful businesses, and is also highly concentrated in a small number of locations around the world.{{Fact|date=October 2008}}

Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care has to be taken in order to prevent larger diamonds from being destroyed in this process and subsequently the particles are sorted by density. Today, diamonds are located in the diamond-rich density fraction with the help of [[X-ray fluorescence]], after which the final sorting steps are done by hand. Before the use of [[X-ray]]s became commonplace, the separation was done with grease belts; diamonds have a stronger tendency to stick to grease than the other minerals in the ore.

Historically diamonds were known to be found only in alluvial deposits in [[southern India]].<ref name=Catelle1>{{cite book | last = Catelle | first = W.R. | title = The Diamond | publisher = John Lane Company | year = 1911}} Page 159 discussion on Alluvial diamonds in India and elsewhere as well as earliest finds </ref> India led the world in diamond production from the time of their discovery in approximately the 9th century BCE<ref name=Ball>{{cite book | last = Ball | first = V. | title = Diamonds, Gold and Coal of India | publisher = London, Truebner & Co. | year = 1881}} Ball was a Geologist in British service. Chapter I, Page 1 </ref> to the mid-18th century AD, but the commercial potential of these sources had been exhausted by the late 18th century and at that time India was eclipsed by Brazil where the first non-Indian diamonds were found in 1725.{{Fact|date=September 2008}}

Diamond production of primary deposits (kimberlites and lamproites) only started in the 1870s after the discovery of the Diamond fields in South Africa. Production has increased over time and now an accumulated total of 4.5 billion carats have been mined since that date.<ref name=giasummer2007>{{cite journal| last = Janse | first= A. J. A. | title= Global Rough Diamond Production Since 1870 | journal= Gems and Gemology | volume= XLIII |issue= Summer 2007| pages=98&ndash;119 |publisher=GIA | year=2007 }}</ref> Interestingly 20% of that amount has been mined in the last 5 years alone and during the last ten years 9 new mines have started production while 4 more are waiting to be opened soon. Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia.<ref name = giasummer2007/>

In the [[United States]], diamonds have been found in [[Arkansas]], [[Colorado]], and [[Montana]].<ref name=DGemGLorenz>{{cite journal| last = Lorenz| first= V. | title=Argyle in Western Australia: The world's richest diamondiferous pipe; its past and future| journal=Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft | volume=56 |issue=1/2| pages=35&ndash;40 |publisher = DGemG | year=2007 }}</ref><ref>{{cite web|url=http://www.montanastandard.com/articles/2004/10/18/featuresbusiness/hjjfijicjbhdjc.txt |title= Microscopic diamond found in Montana | publisher = The Montana Standard | date= 2004-10-17| accessdate = 2008-10-10 }}</ref> In 2004, a startling discovery of a microscopic diamond in the [[United States]]<ref>{{cite web | url = http://www.livescience.com/environment/wyoming_diamond_041019.html | publisher = Livescience.com |accessdate=2008-09-12 | title = Microscopic Diamond Found in Montana | first = Sarah | last = Cooke | date = 2004-10-19<!-- 12:25 -->}}</ref> led to the January 2008 bulk-sampling of [[kimberlite pipes]] in a remote part of [[Montana]].<ref>{{cite web|url=http://www.deltamine.com/release2008-01-08.htm |title=Delta :: News / Press Releases / Publications<!- Bot generated title -> |publisher=Deltamine.com |date= |accessdate=2008-09-12}}</ref>

Today, most commercially viable diamond deposits are in [[Russia]], [[Botswana]], [[Australia]] and the [[Democratic Republic of Congo]].<ref>{{cite web | url = http://gnn.tv/videos/2/The_Diamond_Life | title = The Diamond Life | publisher = Guerrilla News Network | first = Stephen | last = Marshall |coauthors = Shore, Josh |accessdate = 2008-10-10 | date = 2004-10-22}}</ref> In 2005, Russia produced almost one-fifth of the global diamond output, reports the [[British Geological Survey]]. Australia boasts the richest diamondiferous pipe with production reaching peak levels of {{convert|42|MT}} per year in the 1990s.<ref name = DGemGLorenz/>

There are also commercial deposits being actively mined in the [[Northwest Territories]] of [[Canada]], [[Siberia]] (mostly in [[Sakha|Yakutia territory]], for example [[Mir Mine|Mir pipe]] and [[Udachnaya pipe]]), Brazil, and in Northern and Western [[Australia]]. Diamond prospectors continue to search the globe for diamond-bearing [[kimberlite]] and [[lamproite]] pipes.

== Applications ==
[[Image:Mechanical pencil lead spilling out 051907.jpg|thumb|right|200px|Pencil lead for mechanical pencils are made of graphite.]]
[[Image:Charcoal sticks 051907.jpg|left|thumb|200px|Sticks of vine and compressed charcoal.]]
[[Image:Kohlenstofffasermatte.jpg|thumb|left|200px|A cloth of woven carbon filaments]]
[[Image:SiC p1390066.jpg|thumb|right|[[Silicon carbide]] [[single crystal]]]]
[[Image:C60-Fulleren-kristallin.JPG|thumb|left|200px|The ''C''<sub>60</sub> fullerene in crystalline form]]
[[Image:Tungsten carbide.jpg|thumb|right|200px|[[Tungsten carbide]] milling bits]]

Carbon is essential to all known living systems, and without it life as we know it could not exist (see [[alternative biochemistry]]). The major economic use of carbon other than food and wood is in the form of hydrocarbons, most notably the [[fossil fuel]] [[methane]] gas and [[crude oil]] (petroleum). Crude oil is used by the [[petrochemical industry]] to produce, amongst others, [[gasoline]] and [[kerosene]], through a [[distillation]] process, in [[refinery|refineries]]. [[Cellulose]] is a natural, carbon-containing polymer produced by plants in the form of [[cotton]], [[linen]], [[hemp]]. [[Cellulose]] is mainly used for maintaining structure in plants. Commercially valuable carbon polymers of animal origin include [[wool]], [[cashmere]] and [[silk]]. [[Plastics]] are made from synthetic carbon polymers, often with oxygen and nitrogen atoms included at regular intervals in the main polymer chain. The raw materials for many of these synthetic substances come from crude oil.

The uses of carbon and its compounds are extremely varied. It can form [[alloys]] with [[iron]], of which the most common is [[carbon steel]]. [[Graphite]] is combined with [[clay]]s to form the 'lead' used in [[pencil]]s used for [[writing]] and [[drawing]]. It is also used as a [[lubricant]] and a [[pigment]], as a moulding material in [[glass]] manufacture, in [[electrodes]] for dry [[Battery (electricity)|batteries]] and in [[electroplating]] and [[electroforming]], in [[brush]]es for [[electric motors]] and as a [[neutron moderator]] in [[nuclear reactors]].

[[Charcoal]] is used as a drawing material in [[art]]work, for [[grilling]], and in many other uses including iron smelting. Wood, coal and oil are used as [[fuel]] for production of energy and space heating. Gem quality [[diamond]] is used in jewelry, and [[Industrial diamond]]s are used in drilling, cutting and polishing tools for machining metals and stone. Plastics are made from fossil hydrocarbons, and [[carbon fibre]], made by [[pyrolysis]] of synthetic [[polyester]] [[fibre]]s is used to reinforce plastics to form advanced, lightweight [[composite materials]]. [[Carbon fiber]] is made by pyrolysis of extruded and stretched filaments of [[polyacrylonitrile]] (PAN) and other organic substances. The crystallographic structure and mechanical properties of the fiber depend on the type of starting material, and on the subsequent processing. Carbon fibres made from PAN have structure resembling narrow filaments of graphite, but thermal processing may re-order the structure into a continuous rolled sheet {{Fact|date=November 2007}}. The result is fibers with higher [[specific strength|specific tensile strength]] than steel.{{Fact|date=November 2007}}

[[Carbon black]] is used as the black [[pigment]] in [[printing]] [[ink]], artist's oil paint and water colours, [[carbon paper]], automotive finishes, [[India ink]] and [[laser printer]] [[toner]]. [[Carbon black]] is also used as a [[filler]] in [[rubber]] products such as tyres and in [[plastic]] compounds. [[Activated charcoal]] is used as an [[absorbent]] and [[adsorbent]] in [[filter]] material in applications as diverse as [[gas masks]], [[water purification]] and [[kitchen]] [[extractor hood]]s and in medicine to [[Absorption (chemistry)|absorb]] toxins, poisons, or gases from the [[gastrointestinal tract|digestive system]]. Carbon is used in chemical [[reduction]] at high temperatures. [[Coke (fuel)|coke]] is used to reduce iron ore into iron. [[Case hardening]] of steel is achieved by heating finished steel components in carbon powder. [[Carbide]]s of [[silicon carbide|silicon]], [[tungsten carbide|tungsten]], [[boron carbide|boron]] and [[titanium carbide|titanium]], are among the hardest known materials, and are used as [[abrasives]] in cutting and grinding tools. Carbon compounds make up most of the materials used in clothing, such as natural and synthetic [[textiles]] and [[leather]], and almost all of the interior surfaces in the [[built environment]] other than glass, stone and metal.

===Diamonds===
The [[diamond]] industry can be broadly separated into two basically distinct categories: one dealing with gem-grade diamonds and another for industrial-grade diamonds. While a large trade in both types of diamonds exists, the two markets act in dramatically different ways.

A large trade in [[Gemstone|gem]]-grade diamonds exists. Unlike [[precious metal]]s such as [[gold]] or [[platinum]], gem diamonds do not trade as a [[commodity]]: there is a substantial mark-up in the sale of diamonds, and there is not a very active market for resale of diamonds. One hallmark of the trade in gem-quality diamonds is its remarkable concentration: wholesale trade and [[diamond cutting]] is limited to a few locations. 92% of diamond pieces cut in 2003 were in [[Surat]], [[Gujarat]], India.<ref>{{cite web | url = http://www.time.com/time/magazine/article/0,9171,501040419-610100,00.html | title = Uncommon Brilliance - TIME | publisher = Time.com | first = Aravind Adiga | last = Surat |date= 2004-04-12 | accessdate = 2008-09-12}}</ref> Other important centers of diamond cutting and trading are [[Antwerp]], where the [[International Gemological Institute]] is based, [[London]], [[New York City|New York]], [[Tel Aviv]], [[Amsterdam]]. A single company&mdash;[[De Beers]]&mdash;controls a significant proportion of the trade in diamonds. They are based in [[Johannesburg]], [[South Africa]] and [[London]], [[England]].

The production and distribution of diamonds is largely consolidated in the hands of a few key players, and concentrated in traditional diamond trading centers. The most important being [[Antwerp]], where 80% of all rough diamonds, 50% of all cut diamonds and more than 50% of all rough, cut and industrial diamonds combined are handled.{{Fact|date=November 2007}} This makes Antwerp the de facto 'world diamond capital'. [[New York]], however, along with the rest of the United States, is where almost 80% of the world's diamonds are sold, including auction sales. Also, the largest and most unusually shaped rough diamonds end up in New York. The De&nbsp;Beers owns or controls a significant portion of the world's rough diamond production facilities ([[mining|mines]]) and [[Distribution (business)|distribution channels]] for gem-quality diamonds. The company and its subsidiaries own mines that produce some 40 percent of annual world diamond production. At one time it was thought over 80 percent of the world's rough diamonds passed through the [[Diamond Trading Company]] (DTC, a subsidiary of De Beers) in London, but presently the figure is estimated at less than 50 percent. The [[De Beers#Marketing|De Beers diamond advertising campaign]] is acknowledged as one of the most successful and innovative campaigns in history. [[N. W. Ayer & Son]], the advertising firm retained by De Beers in the mid-20th century, succeeded in reviving the American diamond market and opened up new markets, even in countries where no diamond tradition had existed before. N.W. Ayer's multifaceted marketing campaign included [[product placement]], advertising the diamond itself rather than the De Beers brand, and building associations with celebrities and royalty. This coordinated campaign has lasted decades and continues today; it is perhaps best captured by the [[slogan]] "a diamond is forever".

The market for industrial-grade diamonds operates much differently from its gem-grade counterpart. Industrial diamonds are valued mostly for their hardness and heat conductivity, making many of the gemological characteristics of diamond, including clarity and color, mostly irrelevant. This helps explain why 80% of mined diamonds (equal to about 100 million carats or 20,000 kg annually), unsuitable for use as gemstones and known as ''[[bort]]'', are destined for industrial use. In addition to mined diamonds, [[synthetic diamond]]s found industrial applications almost immediately after their invention in the 1950s; another 3 billion carats (600 [[Tonne|metric tons]]) of synthetic diamond is produced annually for industrial use. The dominant industrial use of diamond is in cutting, drilling, grinding, and polishing. Most uses of diamonds in these technologies do not require large diamonds; in fact, most diamonds that are gem-quality except for their small size, can find an industrial use. Diamonds are embedded in drill tips or saw blades, or ground into a powder for use in grinding and polishing applications. Specialized applications include use in laboratories as containment for [[Pressure experiment|high pressure experiments]] (see [[diamond anvil cell]]), high-performance [[bearing (mechanical)|bearings]], and limited use in specialized [[window]]s. With the continuing advances being made in the production of synthetic diamonds, future applications are beginning to become feasible. Garnering much excitement is the possible use of diamond as a [[semiconductor]] suitable to build [[integrated circuit|microchip]]s from, or the use of diamond as a [[heat sink]] in [[electronics]].

== Precautions ==
Pure carbon has extremely low toxicity and can be handled and even ingested safely in the form of graphite or charcoal. It is resistant to dissolution or chemical attack, even in the acidic contents of the digestive tract, for example. Consequently if it gets into body tissues it is likely to remain there indefinitely. [[Carbon black]] was probably one of the first pigments to be used for [[tattoo]]ing, and [[Ötzi the Iceman]] was found to have carbon tattoos that survived during his life and for 5200 years after his death.<ref>{{cite journal | first = Leopold | coauthors = Moser, Maximilian; Spindler, Konrad; Bahr, Frank; Egarter-Vigl, Eduard; Dohr, Gottfried | last = Dorfer | year = 1998 | title = 5200-year old acupuncture in Central Europe? | journal = Science | volume = 282 | pages = 242&ndash;243 | doi = 10.1126/science.282.5387.239f}}</ref> However, inhalation of coal dust or soot ([[carbon black]]) in large quantities can be dangerous, irritating lung tissues and causing the congestive [[lung]] disease [[coalworker's pneumoconiosis]]. Similarly, diamond dust used as an abrasive can do harm if ingested or inhaled. Microparticles of carbon are produced in diesel engine exhaust fumes, and may accumulate in the lungs.<ref>{{cite journal | last = Donaldson | first = K | coauthors = Stone, V.; Clouter, A.; Renwick, L.; MacNee, W. | year = 2001 | title = Ultrafine particles | journal = Occupational and Environmental Medicine | volume = 58 | pages = 211&ndash;216 | url = http://oem.bmj.com/cgi/content/extract/58/3/211}}</ref> In these examples, the harmful effects may result from contamination of the carbon particles, with organic chemicals or heavy metals for example, rather than from the carbon itself.

Carbon may also burn vigorously and brightly in the presence of air at high temperatures, as in the [[Windscale fire]], which was caused by sudden release of stored [[Wigner energy]] in the graphite core. Large accumulations of coal, which have remained inert for hundred of millions of years in the absence of oxygen, may [[spontaneous combustion|spontaneously combust]] when exposed to air, for example in coal mine waste tips.
The great variety of carbon compounds include such lethal poisons as [[tetrodotoxin]], the [[lectin]] [[ricin]] from seeds of the [[castor oil plant]] ''[[Ricinus communis]]'', [[Cyanide poisoning|cyanide]] (CN<sup>-</sup>) and [[Carbon monoxide poisoning|carbon monoxide]]; and such essentials to life as [[glucose]] and [[protein]].

== See also ==
<div style="-moz-column-count:2; column-count:2;">
* [[Carbon chauvinism]]
* [[Carbon footprint]]
* [[Low-carbon economy]]
* [[Organic chemistry]]
* [[Timeline of carbon nanotubes]]
</div>

== References ==
{{reflist|2}}
* ''[http://lbruno.home.cern.ch/lbruno/documents/Bibliography/LHC_Note_78.pdf On Graphite Transformations at High Temperature and Pressure Induced by Absorption of the LHC Beam]'', J.M. Zazula, 1997

== External links ==
{{Commons|Carbon}}
{{wiktionarypar|carbon}}
* [http://www.youtube.com/watch?v=wmC8Dg4n-ZA Carbon - Periodic Table of Videos]
* [http://www.britannica.com/eb/article-80956/carbon-group-element Carbon on Britannica]
* [http://www.webelements.com/carbon/ WebElements.com &ndash; Carbon]
* [http://www.chemicool.com/elements/carbon.html Chemicool.com &ndash; Carbon]
* [http://education.jlab.org/itselemental/ele006.html It's Elemental &ndash; Carbon]
* [http://invsee.asu.edu/nmodules/Carbonmod/everywhere.html Extensive Carbon page at asu.edu]
* [http://electrochem.cwru.edu/ed/encycl/art-c01-carbon.htm Electrochemical uses of carbon]
* [http://www.compchemwiki.org/index.php?title=Carbon Computational Chemistry Wiki]
* [http://www.forskning.no/Artikler/2006/juni/1149432180.36 Carbon - Super Stuff. Animation with sound and interactive 3D-models.]
* [http://www.bbc.co.uk/radio4/history/inourtime/inourtime_20060615.shtml BBC Radio 4 series "In Our Time", on ''Carbon, the basis of life'', 15 June 2006]
* [http://canadaconnects.ca/chemistry/1009/ Introduction to Carbon Properties geared for High School students.]
* [http://octettruss.kilu.de/diamond.html diamond 3D animation]

{{Compact periodic table}}

[[Category:Carbon| ]]
[[Category:Carbonate minerals]]
[[Category:Carbon forms| ]]
[[Category:Chemical elements]]
[[Category:Organic minerals]]

{{Link FA|lmo}}
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[[af:Koolstof]]
[[als:Kohlenstoff]]
[[ar:كربون]]
[[ast:Carbonu]]
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[[bn:কার্বন]]
[[zh-min-nan:C (goân-sò͘)]]
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[[et:Süsinik]]
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[[gu:કાર્બન]]
[[ko:탄소]]
[[haw:Kalepona]]
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[[hi:कार्बन]]
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[[kn:ಇಂಗಾಲ]]
[[sw:Kaboni]]
[[ht:Kabòn]]
[[ku:Karbon]]
[[la:Carbonium]]
[[lv:Ogleklis]]
[[lb:Kuelestoff]]
[[lt:Anglis]]
[[li:Koolstof]]
[[ln:Kaboni]]
[[jbo:tabno]]
[[lmo:Carbòni]]
[[hu:Szén]]
[[mk:Јаглерод]]
[[ml:കാര്‍ബണ്‍]]
[[mt:Karbonju]]
[[mi:Waro]]
[[mr:कार्बन]]
[[ms:Karbon]]
[[mn:Нүүрстөрөгч]]
[[nah:Tecolli]]
[[myv:Седь]]
[[nl:Koolstof]]
[[ja:炭素]]
[[no:Karbon]]
[[nn:Karbon]]
[[nov:Karbo]]
[[oc:Carbòni]]
[[uz:Uglerod]]
[[pa:ਕਾਰਬਨ]]
[[nds:Kohlenstoff]]
[[pl:Węgiel (pierwiastek)]]
[[pt:Carbono]]
[[ksh:Kohlenstoff]]
[[ro:Carbon]]
[[qu:K'illimsayaq]]
[[ru:Углерод]]
[[sq:Karboni]]
[[scn:Carbòniu]]
[[simple:Carbon]]
[[sk:Uhlík]]
[[sl:Ogljik]]
[[sr:Угљеник]]
[[sh:Ugljenik]]
[[su:Karbon]]
[[fi:Hiili]]
[[sv:Kol]]
[[tl:Karbon]]
[[ta:கரிமம்]]
[[te:కార్బన్]]
[[th:คาร์บอน]]
[[vi:Cacbon]]
[[tg:Карбон]]
[[tr:Karbon]]
[[uk:Вуглець]]
[[wa:Carbone]]
[[vls:Carboun]]
[[wuu:碳]]
[[yi:קוילנשטאף]]
[[zh-yue:碳]]
[[bat-smg:Onglis]]
[[zh:碳]]

Revision as of 15:46, 17 November 2008

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