clear (diamond) & black (graphite)

Spectral lines of Carbon
General properties
Name, symbol, number carbon, C, 6
Pronunciation /ˈkɑːrbən/
Element category nonmetal
Group, period, block 142, p
Standard atomic weight 12.011(1) g/mol
Electron configuration [He] 2s2 2p2
Electrons per shell 2, 4 (Image)
Physical properties
Phase solid
Density (near r.t.) amorphous: 1.8–2.1 g/cm3
Density (near r.t.) diamond: 3.515 g/cm3
Density (near r.t.) graphite: 2.267 g/cm3
Sublimation point 3915 K, 3642 °C, 6588 °F
Triple point 4600 K (4327°C), 10800 kPa
Heat of fusion 117 (graphite) kJ/mol
Specific heat capacity (25 °C) 6.155 (diamond)
8.517 (graphite) J/(mol·K)
Atomic properties
Oxidation states 4, 3, 2, 1, 0, −1, −2, −3, −4
Electronegativity 2.55 (Pauling scale)
Ionization energies
1st: 1086.5 kJ/mol
2nd: 2352.6 kJ/mol
3rd: 4620.5 kJ/mol
Covalent radius 77(sp³), 73(sp²), 69(sp) pm
Van der Waals radius 170 pm
Crystal structure diamond
Crystal structure note (diamond, clear)
Magnetic ordering diamagnetic
Thermal conductivity (300 K) 900-2300 (diamond)
119-165 (graphite) W/(m·K)
Thermal expansion (25 °C) 0.8 (diamond) µm/(m·K)
Speed of sound (thin rod) (20 °C) 18350 (diamond) m/s
Young's modulus 1050 (diamond) GPa
Shear modulus 478 (diamond) GPa
Bulk modulus 442 (diamond) GPa
Poisson ratio 0.1 (diamond)
Mohs hardness 10 (diamond)
1-2 (graphite)
CAS registry number 7440-44-0
Most stable isotopes
Main article: Isotopes of carbon
iso NA half-life DM DE (MeV) DP


11C syn 20 min β+ 0.96 11B
12C 98.9% 12C is stable with 6 neutrons
13C 1.1% 13C is stable with 7 neutrons
14C trace 5730 y β 0.15 14N

Carbon is a very important chemical element, with a chemical symbol of C. All known life on Earth is made from it. Carbon has atomic mass 12 and atomic number 6. It is a nonmetal, meaning that it is not a metal.

Why it is important?

Carbon, hydrogen, nitrogen, oxygen, and some other elements like sulfur and phosphorus together form most life on earth (see Organic chemistry and List of biologically important elements). Carbon forms a very large number of organic compounds because it can form strong bonds with itself and with other elements. Because of the amounts of carbon living things have, all organic things are considered "carbon-based". Also, each carbon atom can form 4 single covalent bonds. Many carbon atoms linked together with hydrogen atoms form plastic. Carbon is the only element that can form long chain-shaped molecules. When iron is heated up with carbon, hard steel is formed.


The name of carbon comes from Latin carbo, meaning charcoal. In many foreign languages the words for carbon, coal and charcoal are synonyms.

Types of carbon

Carbon in nature is found in three forms called allotropes: diamond, graphite, and fullerenes. Graphite, with clay, is in pencils. 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 natural mineral. Fullerenes are a "soccer ball" shape of carbon. They are mostly of interest to science. A special, man-made, tube-shaped allotrope of carbon is the carbon nanotube. Carbon nanotubes are very hard, so they might be used in armor. Nanotubes might be useful in nanotechnology. There are 10 million known carbon compounds.

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

Chemistry of carbon

A whole type of Chemistry, organic chemistry, is about carbon and its compounds. Carbon makes many types of compounds. Hydrocarbons are molecules with carbon and hydrogen. Methane, Propane, and many other fuels are hydrocarbons. Many of the substances that people use daily are organic compounds.

Radiocarbon dating

A radioactive isotope of 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 the half-life (how long it takes for half of a radioactive isotope to go away) of carbon-14 is 5730 years, scientists can 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 old stars. Carbon is the fourth most common element in the sun. The atmospheres of Venus and Mars are mostly Carbon dioxide.

Carbon is important to the human body and other living 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 (molecules used in life).

Most of the carbon on Earth is coal. Graphite is in many (typically desert) areas, including Sri Lanka, Madagascar, and Russia. Diamonds are rare and are found largely in Africa. Carbon is also in some meteorites.

Related pages


Carbon for Kids. Kiddle Encyclopedia.