Periodic Table


Atomic number: 6
Atomic weight: 12.0107
Symbol: C
Group number: 14
Electronic configuration: [He].2s2.2p2


Carbon is a Group 14 element. Carbon is distributed very widely in nature. It is found in abundance in the sun, stars, comets, and atmospheres of most planets. The atmosphere of Mars contains 96 % CO2.

Carbon is found free in nature in three allotropic forms: amorphous, graphite, and diamond. Graphite is one of the softest known materials while diamond is one of the hardest. Carbon, as microscopic diamonds, is found in some meteorites. Natural diamonds are found in kimberlite of ancient volcanic "pipes" such as found in South Africa. Diamonds are also recovered from the ocean floor off the Cape of Good Hope.

In combination, carbon is found as carbon dioxide in the atmosphere of the earth and dissolved in all natural waters. It is a component of rock masses as carbonates of calcium (limestone), magnesium, and iron. Coal, petroleum, and natural gas are chiefly hydrocarbons. Carbon is unique among the elements in the vast number of variety of compounds it can form. Organic chemistry, a 1/112th subset of inorganic chemistry, is the study of carbon and its compounds. While silicon might take the place of carbon in forming a host of related compounds, it is not possible currently to form stable compounds with very long chains of silicon atoms.

In 1961 the International Union of Pure and Applied Chemistry (IUPAC) adopted the isotope 12C as the basis for atomic weights. Carbon-14, 14C, an isotope with a half-life of 5730 years, is used to date such materials as wood, archeological specimens, etc. Carbon-13, 13C, is particularly useful for isotopic labelling studies since it is not radioactive, but is a spin I = 1/2 nucleus and therefore a good NMR nucleus.

General information

Discoveror: Known since ancient times although not recognised as an element until much later.
Date discovered:
Discovered at: not known
Meaning of name: From the Latin word "carbo" meaning "charcoal"

Physical data

Standard state: solid at 298 K
Colour: graphite is black, diamond is colourless
Density of solid at ambient temperature/kg m-3: 2267
Molar volume/cm3: 5.29

Radii /pm

Atomic: 67
Covalent (single bond):
Pauling radius for the ion [C]-: 414

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius64.664.4no datano data


Both values are quoted on the Pauling scale.

Pauling: 2.55
Allred Rochow: 2.50

Crystal Structure

structure: hcp (hexagonal close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 4273
boiling point: 4300

Enthalpies /kJ mol-1

fusion: 117
vaporization: 715

single bond enthalpies:
C-F C-Cl C-Br C-I C-C
485 327 285 213 607

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
12C12.000000000*98.90 (3)
13C13.003354826 (17)1.10 (3)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/C.html