Symbol C. The element with atomic number 6 and relative atomic mass 12.01, which is at the top of Group 14. As carbon-based life forms, we have assigned carbon the most important place in chemistry: the study of carbon constitutes one of the three major branches of the subject, organic chemistry.
The element itself has three allotropes. Two have been familiar since prehistory, graphite and diamond. The third allotrope, buckminsterfullerene, was discovered in 1990. Several of the apparently amorphous forms of carbon, such as charcoal, have a microscopic structure like graphite\'s. Carbon is a nonmetal; its most unusual physical property is that graphite is a conductor, a fact that leads to its use as an electrode material for electrolysis.
The most important oxidation number for carbon is +4, as in carbon dioxide, in which two oxygen atoms form two bonds each to the carbon atom. Although the concept of oxidation number is much less useful in organic chemistry, the vast majority of organic compounds also have carbon forming four covalent bonds with other atoms.
Carbon dioxide, CO{TAG(tag=>sub)}2{TAG}, is acidic but carbon monoxide, CO, is noticeably less so. Both oxides are of considerable importance both in everyday life and in industry.
There is a whole range of halides, generally called halogenoalkanes. Tetrachloromethane and trichloromethane have been important solvents, although their use is declining as they are suspected as carcinogens.See carbon cycle; photosynthesis; radiocarbon dating. |
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