C
CARBON
(L. carbo, charcoal)
C at. wt. 12 exactly (C12)
at. wt. (natural carbon) 12.011100
at. no. 6
graphite sublimes at 3367 ±25°C
m.p. 3550°C
b.p. 4827°C
sp. gr. amorphous 1.8-2.1
sp. gr. graphite 1.9-2.3
sp. gr. diamond 3.15-3.53 (Gem 3.513) (25°C)
valence 2, 3, or 4.
Electronic configuration
| SHELL |
K |
L |
M |
N |
O |
P |
Q |
| SUB SHELL |
He |
Neon |
Argon |
Krypton |
Xenon |
Radon |
Eka-radon |
| 1s |
2s 2p |
3s 3p |
3d 4s 4p |
4d 5s 5p |
4f 5d 6s 6p |
5f 6d 7s 7p |
| Carbon
|
1s22s22p2 |
|
|
|
|
|
| Symbol
|
3P0 |
Carbon, an element of prehistoric discoyery, is very widely
distributed in nature, It is found in abundance in the sun,
stars, comets, and atmospheres of most planets. Carbon in
the form of microscopic diamonds is found in some meteor-
ites. Natural diamonds are found in Kimberlite of ancient
volcanic "pipes," such as found in South Africa, Arkansas,
and elsewhere. Diamonds are now also being recovered from
the ocean floor off the Cape of Good Hope. About 30% of
all industrial diamonds used in the U.S. are now made
synthetically. The energy of the sun and stars can be attributed
at least in part to the well-known carbon-nitrogen cycle.
Carbon is found free in nature in three allotropic forms:
amorphous, graphite, and diamond. A fouith form, known as
"white" carbon, is now thought to exist. Graphite is one of
the softest known materials while diamond is one of the
hardest. Graphite exists in two forms: alpha 4nd beta. These
have identical physical properties, except for their crystal
structure. Naturally occurring graphites are reported to
contain as much as 30 % of the rhombohedral (beta) form,
whereas synthetic materials contain only the alpha form.
The hexagonal alpha type can be converted to the beta by
mechanical treatment, and the beta form reverts to the alpha
on heating it above 10000C. In 1969 a new allotropic form of
carbon was produced during the sublimation of pyrolytic
graphite at low pressures. Under free-vaporization condi-
tions above 25500K, "white" carbon forms as small trans-
parent crystals on the edges of the basal planes of graphite.
The interplanar spacings of "white" carbon are identical to
those of a carbon form noted in the graphitic gneiss from the
Ries (meteoritic) Crater of Germany. "White" carbon is a
transparent birefringent material. Little information is
presently available about this allotrope. 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
great rock masses in the form of 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 and variety of com
pounds it can form. With hydrogen, oxygen, and nitrogen,
and other elements, it forms an infinite number of com-
pounds, carbon atom often being linked to carbon atom.
There are upwards of a million or more known carbon
compounds, many thousands of which are vital to organic
and life processes. Without carbon, the basis for life would
be impossible. While it has been thought that silicon might
take the place of carbon in forming a host of similar com-
pounds, it is now not p6ssible to form stable compounds
with very long chains of silicon atoms. Some of the most
important compounds of carbon are: carbon dioxide (C02),
carbon monoxide (CO), carbon disulfide (C52), chloroform
(CHCl3), carbon tetrachloride (CCI4), methane (CH4),
ethylene (C2H4), acetylene (C2H2), benzene (C6H6), ethyl
alcohol (C2H5OH), acetic acid (CH3COOH), and their
derivatives. Carbon has seven isotopes. In 1961 the Inter-
national Union of Pure and Applied Chemistry adopted the
isotope carbon- 12 as the basis for atomic weights. Carbon-
14, an isotope with a half-life of 5730 yrs, has been widely
used to date such materials as wood, archeological speci-
mens, etc. Carbon-13 is now commercially available at a
cost of $700/gm.
© 1999 F. Davies
Delphi O.E.M. Co.
All rights reserved
