A nonmetallic tetravalent element, atomic no. 6, atomic wt. 12.011; the major bioelement. It has two natural isotopes, 12C and 13C (the former, set at 12.00000, being the standard for all molecular weights), and two artificial, radioactive isotopes of interest, 11C and 14C. The element occurs in three pure forms (diamond, graphite, and in the fullerines), in amorphous form (in charcoal, coke, and soot), and in the atmosphere as CO2. Its compounds are found in all living tissues, and the study of its vast number of compounds constitutes most of organic chemistry. [L. carbo, coal]