Chemical element, symbol C and atomic number 6 / From Wikipedia, the free encyclopedia

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Carbon (from Latin carbo 'coal') is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table.[14] Carbon makes up about 0.025 percent of Earth's crust.[15] Three isotopes occur naturally, 12C and 13C being stable, while 14C is a radionuclide, decaying with a half-life of about 5,730 years.[16] Carbon is one of the few elements known since antiquity.[17]

Quick facts: Carbon, Allotropes, Appearance, Standard atom...
Carbon, 6C
Graphite (left) and diamond (right), two allotropes of carbon
Allotropesgraphite, diamond and more (see Allotropes of carbon)
  • graphite: black, metallic-looking
  • diamond: clear
Standard atomic weight Ar°(C)
  • [12.0096, 12.0116]
  • 12.011±0.002 (abridged)[1]
Carbon in the periodic table


Atomic number (Z)6
Groupgroup 14 (carbon group)
Periodperiod 2
Block  p-block
Electron configuration[He] 2s2 2p2
Electrons per shell2, 4
Physical properties
Phase at STPsolid
Sublimation point3915 K (3642 °C, 6588 °F)
Density (near r.t.)amorphous: 1.8–2.1 g/cm3[2]
graphite: 2.267 g/cm3
diamond: 3.515 g/cm3
Triple point4600 K, 10,800 kPa[3][4]
Heat of fusiongraphite: 117 kJ/mol
Molar heat capacitygraphite: 8.517 J/(mol·K)
diamond: 6.155 J/(mol·K)
Atomic properties
Oxidation states−4, −3, −2, −1, 0, +1,[5] +2, +3,[6] +4[7] (a mildly acidic oxide)
ElectronegativityPauling scale: 2.55
Ionization energies
  • 1st: 1086.5 kJ/mol
  • 2nd: 2352.6 kJ/mol
  • 3rd: 4620.5 kJ/mol
  • (more)
Covalent radiussp3: 77 pm
sp2: 73 pm
sp: 69 pm
Van der Waals radius170 pm
Color lines in a spectral range
Spectral lines of carbon
Other properties
Natural occurrenceprimordial
Crystal structuregraphite: simple hexagonal
Simple hexagonal crystal structure for graphite: carbon

Crystal structurediamond: face-centered diamond-cubic
Diamond cubic crystal structure for diamond: carbon

Speed of sound thin roddiamond: 18,350 m/s (at 20 °C)
Thermal expansiondiamond: 0.8 µm/(m⋅K) (at 25 °C)[8]
Thermal conductivitygraphite: 119–165 W/(m⋅K)
diamond: 900–2300 W/(m⋅K)
Electrical resistivitygraphite: 7.837 µΩ⋅m[9]
Magnetic orderingdiamagnetic[10]
Molar magnetic susceptibilitydiamond: −5.9×10−6 cm3/mol[11]
Young's modulusdiamond: 1050 GPa[8]
Shear modulusdiamond: 478 GPa[8]
Bulk modulusdiamond: 442 GPa[8]
Poisson ratiodiamond: 0.1[8]
Mohs hardnessgraphite: 12
diamond: 10
CAS Number
  • atomic carbon: 7440-44-0
  • graphite: 7782-42-5
  • diamond: 7782-40-3
DiscoveryEgyptians and Sumerians[12] (3750 BCE)
Recognized as an element byAntoine Lavoisier[13] (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 1 ppt (11012) 5.70×103 y β 14N
Symbol_category_class.svg Category: Carbon
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Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Carbon's abundance, its unique diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth, enables this element to serve as a common element of all known life. It is the second most abundant element in the human body by mass (about 18.5%) after oxygen.[18]

The atoms of carbon can bond together in diverse ways, resulting in various allotropes of carbon. Well-known allotropes include graphite, diamond, amorphous carbon and fullerenes. The physical properties of carbon vary widely with the allotropic form. For example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known. Graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials. All carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form at standard temperature and pressure. They are chemically resistant and require 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 transition metal carbonyl complexes. The largest sources of inorganic carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil, and methane clathrates. Carbon forms a vast number of compounds, with about two hundred million having been described and indexed;[19] and yet that number is but a fraction of the number of theoretically possible compounds under standard conditions.