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There are nearly ten million carbon compounds that are known to science and many thousands of these are vital to life processes and very economically important organic-based reactions. This element is abundant in the sun, stars, comets, and in the atmospheres of most planets. Some meteorites contain microscopic diamonds that were formed when the solar system was still a protoplanetary disk. In combination with other elements, carbon is found the earth's atmosphere and dissolved in all bodies of water. With smaller amounts of calcium, magnesium, and iron, it is a major component of very large masses carbonate rock ( limestone, dolomite, marble etc.). When combined with hydrogen, carbon form coal, petroleum, and natural gas which are called hydrocarbons.
Graphite is found in large quantities in New York and Texas, the United States; Russia; Mexico; Greenland and India.
Natural diamonds occur in the mineral kimberlite found in ancient volcanic "necks," or "pipes". Most diamond deposits are in Africa, notably in South Africa, Namibia, Botswana, the Republic of the Congo and Sierra Leone. There are also deposits in Canada, the Russian Arctic, Brazil and in Northern and Western Australia.
(See also organic chemistry.)
The most prominent oxide of carbon is carbon dioxide, CO2. This is a minor component of the Earth's atmosphere, produced and used by living things, and a common volatile elsewhere. In water it forms trace amounts of carbonic acid, H2CO3, but as most compounds with multiple single-bonded oxygens on a single carbon it is unstable. Through this intermediate, though, resonance-stabilized carbonate ions are produced. Some important minerals are carbonates, notably calcite. Carbon disulfide, CS2, is similar.
The other oxides are carbon monoxide, CO, and the uncommon carbon suboxide, C3O2. Carbon monoxide is formed by incomplete combustion, and is a colorless, odorless gas. The molecules each contain a triple bond and are fairly polar, resulting in a tendency to bind permanently to hemoglobin molecules, so that the gas is highly poisonous. Cyanide, CN-, has a similar structure and behaves a lot like a halide ion; the nitride cyanogen, (CN)2, is related.
With strong metals carbon forms either carbides, C-, or acetylides, C22-; these are associated with methane and acetylene, both incredibly pathetic acids. All in all, with an electronegativity of 2.5, carbon prefers to form covalent bonds. A few carbides are covalent lattices, like carborundum, SiC, which resembles diamond.
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