Carbon

Carbon,₀₀C

Graphite (left) and diamond (right), two allotropes of carbon
Carbon
Allotropes	graphite,diamondand more (seeAllotropes of carbon)
Appearance	graphite: black diamond: clear
Standard atomic weightAr°(C)
	[12.0096,12.0116]
Carbon in theperiodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson – ↑ C ↓ Si boron←carbon→nitrogen
Group	group 14 (carbon group)
Period	period 2
Block	p-block
Electron configuration	[He] 2s22p2
Electrons per shell	2, 4
Physical properties
PhaseatSTP	solid
Sublimation point	3915 K ​(3642 °C, ​6588 °F)
Density(nearr.t.)	amorphous: 1.8–2.1 g/cm3 graphite: 2.267 g/cm3 diamond: 3.515 g/cm3
Triple point	4600 K, ​10,800 kPa
Heat of fusion	graphite: 117kJ/mol
Molar heat capacity	graphite: 8.517 J/(mol·K) diamond: 6.155 J/(mol·K)
Atomic properties
Oxidation states	−4,−3,−2,−1,0,+1,+2,+3,+4(a mildlyacidicoxide)
Electronegativity	Pauling scale: 2.55
Ionization energies	1st: 1086.5 kJ/mol 2nd: 2352.6 kJ/mol 3rd: 4620.5 kJ/mol (more)
Covalent radius	sp3:77 pm sp2:73 pm sp: 69pm
Van der Waals radius	170 pm
Spectral linesof carbon
Other properties
Natural occurrence	primordial
Crystal structure	graphite: ​simple hexagonal (black)
Crystal structure	diamond: ​face-centered diamond-cubic (clear)
Speed of soundthin rod	diamond: 18,350 m/s (at 20 °C)
Thermal expansion	diamond: 0.8 µm/(m⋅K) (at 25 °C)
Thermal conductivity	graphite: 119–165 W/(m⋅K) diamond: 900–2300 W/(m⋅K)
Electrical resistivity	graphite: 7.837 µΩ⋅m
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	−5.9·10−6(graph.) cm3/mol
Young's modulus	diamond: 1050 GPa
Shear modulus	diamond: 478 GPa
Bulk modulus	diamond: 442 GPa
Poisson ratio	diamond: 0.1
Mohs hardness	graphite: 1–2 diamond: 10
CAS Number	7440-44-0
History
Discovery	EgyptiansandSumerians(3750 BCE)
Recognized as an element by	Antoine Lavoisier(1789)
Isotopes of carbon
Main isotopes Decay abun­dance half-life(t1/2) mode pro­duct 11C synth 20.34 min β+ 11B 12C 98.9% stable 13C 1.06% stable 14C 1ppt(​1⁄1012) 5.70×103y β− 14N

Carbonis a very importantchemical element,with achemical symbolofC.All knownlifeonEarthneeds it to survive. Carbon hasatomic mass12 andatomic number6. It is anonmetal,meaning that it is not ametal.

Whenironisalloyedwith carbon, hardsteelis formed. Carbon in the form ofcoalis an importantfuel.

Chemistry of carbon

A whole type of chemistry, calledorganic chemistry,is about carbon and itscompounds.Carbon makes many types of compounds.Hydrocarbonsare molecules with carbon and hydrogen.Methane,Propane,and many otherfuelsare hydrocarbons. Many of the substances that people use daily are organic compounds.

Carbon,hydrogen,nitrogen,oxygen,and some other elements likesulfurandphosphorustogether form most life onearth(seeList of biologically important elements). Carbon forms a very large number oforganic compoundsbecause it can form strongbondswith itself and with other elements. Because of the amounts of carbon living things have, all organic things are considered "carbon-based".

Each carbon atom usually forms fourchemical bonds,which are strong connections to other atoms to formmolecules.The kind of bond that carbon makes is called acovalent bond.These bonds allow carbon to form many kinds of small and large molecules. A molecule ofmethaneis the smallest; it has fourhydrogenatoms bonded to carbon. The bonds can bedouble bonds,meaning that two bonds form between carbon and another atom to make a stronger connection. For example,carbon dioxidehas twooxygenatoms, and each one is double bonded to carbon. Carbon can even form three bonds with another atom, called atriple bond.For example, in the gasacetylenecarbon forms a triple bond with another carbon atom.

By bonding to other carbon atoms, carbon can form long chain-shapedmolecules,calledpolymers,such asplasticsandproteins.Atoms of other elements can be part of the long polymer chains, often nitrogen or oxygen.

Pure carbon formsdiamondby bonding to four other carbon atoms in athree dimensionalcrystal.It formsgraphiteby bonding to three other carbon atoms to form thin flat layers.

Etymology

The name of carbon comes fromLatincarbo,meaningcharcoal.In many foreign languages the words for carbon,coaland charcoal are synonyms.

Types of carbon

See the main article:Allotropes of carbon

Carbon innatureis found in three forms calledallotropes:diamond,graphite,andfullerenes.Graphite, withclay,is inpencils.It is very soft. The carbon atoms in it make rings, which are on top of each other and slide very easily. Diamonds are the hardest naturalmineral.Fullerenes are a "soccerball "shape of carbon. They are mostly of interest toscience.A special, man-made, tube-shaped allotrope of carbon is thecarbon nanotube.Carbon nanotubes are very hard, so they might be used inarmor.Nanotubes might be useful innanotechnology.

There are 10 million known carboncompounds.

Some forms of carbon: a)diamond;b)graphite;c)lonsdaleite;d-f)fullerenes(C60, C540, C70); g)amorphous carbon;h)carbon nanotube.

Radiocarbon dating

See the main article:Radiocarbon dating

Aradioactiveisotopeof carbon, carbon-14, can be used to figure out how old some objects are or when something died. As long as something is on the surface of the earth and taking in carbon, the amount of carbon-14 stays the same. When an object stops taking in carbon, the carbon-14 amount goes down. Because thehalf-life(how long it takes for half of a radioactive isotope to go away) of carbon-14 is 5730 years,scientistscan see how old the object is by how much carbon-14 is left.

Where carbon is

Carbon is in many places in the universe. It was first made in oldstars.Carbon is the fourth most common element in thesun.TheatmospheresofVenusandMarsare mostlycarbon dioxide.

Carbon is important to thehuman bodyand otherliving things,and it is the second most common element in the human body, at 23% of all body weight.It is also a key part of many biological molecules (moleculesused in life).

Most of the carbon on Earth iscoal.Graphiteis in many (typicallydesert) areas, includingSri Lanka,Madagascar,andRussia.Diamonds are rare and are found largely inAfrica.Carbon is also in some meteorites.

Related pages

• List of common elements
• Carbon cycle
  • Carbon sequestration

Other websites

• Carbon at Webelements