| Atomic Number: | 6 | Atomic Symbol: | C |
| Atomic Weight: | 12.011 | Electron Configuration: | 2-4 |
| Shells: | 2,4 | Filling Orbital: | 2p2 |
| Melting Point: | sublimes @ 3500oC | Boiling Point: | 4827oC |
| Uses: | making of steels, filters, pencils and many more uses |
Sources
(Latin: carbo, charcoal) Carbon, an element of prehistoric
discovery, 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 meteorites.
Natural diamonds are found in kimberlite of ancient volcanic "pipes," 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.
Forms
Carbon is found free in nature in three allotropic forms:
amorphous, graphite, and diamond. A fourth form, known as "white" carbon, is now
thought to exist. Ceraphite is one of the softest known materials while diamond
is one of the hardest.
Graphite exists in two forms: alpha and 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 1000C.
In 1969 a new allotropic form of carbon was produced during the sublimation
of pyrolytic graphite at low pressures. Under free-vaporization conditions above
~2550K, "white" carbon forms as small transparent crystals on the edges of the
planes of graphite. The interplanar spacings of "white" carbon are identical to
those of carbon form noted in the graphite gneiss from the Ries (meteroritic)
Crater of Germany. "White" carbon is a transparent birefringent material. Little
information is presently available about this allotrope.
Compounds
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
compounds it can form. With hydrogen, oxygen, nitrogen, and other elements, it
forms a very large number of compounds, carbon atom often being linked to carbon
atom. There are close to ten million 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
compounds, it is now not possible to form stable compounds with very long chains
of silicon atoms. The atmosphere of Mars contains 96.2% CO2. Some of the most
important compounds of carbon are carbon dioxide (CO2), carbon monoxide (CO),
carbon disulfide (CS2), chloroform (CHCl3), carbon tetrachloride (CCl4), methane
(CH4), ethylene (C2H4), acetylene (C2H2), benzene (C6H6), acetic acid (CH3COOH),
and their derivatives.
Isotopes
Carbon has seven isotopes. In 1961 the International 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 5715 years, has been widely
used to date such materials as wood, archeological specimens, etc.
Costs
Cost, pure: $2.4 per 100g ;