carbon

• Description
• General information
• Physical data
• Radii
• Electronegativities
• Solid state structure
• Temperatures
• Enthalpies
• Ionization Enthalpies
• Isotopes
• Further information

Description

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 (R_max)

orbital	s	p	d	f
radius	64.6	64.4	no data	no data

Electronegativities

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
1st	1086.4
2nd	2352.6
3rd	4620.5
4th	6223
5th	37830
6th	47270

Isotopes

This section gives some data for naturally occurring isotopes.

Nominal mass	Accurate mass	% natural abundance
12C	12.000000000*	98.90 (3)
13C	13.003354826 (17)	1.10 (3)

Further Information

• Additional information about WebElements 1.2.2
• This is a licensed copy (here is the full list) of WebElements 1.2.2 and contains a subset of the material contained within the main version of WebElements (version 2)
• For further information please try WebElements version 2
• Sheffield Chemdex: perhaps the largest internet chemistry directory
• Sheffield Chemputer: interactive chemistry calculators on the WWW