![]() ![]() Carbon-14, which has a half-life of 5,730 years, is a naturally occurring isotope that can also be produced in a nuclear reactor. Carbon-13 absorbs radio waves and is used in nuclear magnetic resonance spectrometry to study organic compounds. Carbon-12 was chosen by IUPAC in 1961 as the basis for atomic weights it is assigned an atomic mass of exactly 12 atomic mass units. It is a constituent of all organic matter.Ĭarbon has 13 known isotopes, which have from 2 to 14 neutrons in the nucleus and mass numbers from 8 to 20. Carbon has the capacity to act chemically both as a metal and as a nonmetal. A fifth form, white carbon, is believed to exist. The most prominent of the fullerenes is buckminsterfullerene, a spheroidal molecule, resembling a soccer ball, consisting of 60 carbon atoms. A fourth form contains the fullerenes, stable molecules consisting of carbon atoms that arrange themselves into 12 pentagonal faces and any number greater than 1 of hexagonal faces. In a third form, the so-called amorphous carbon, the element occurs partly free and partly combined with other elements charcoal, coal, coke, lampblack, peat, and lignite are some sources of amorphous carbon. Diamond, a second crystalline form, is the hardest substance known. One form, graphite, is a very soft, dark gray or black, lustrous material with either a hexagonal or rhombohedral crystalline structure. Carbon is found free in nature in at least four distinct forms (see allotropy). ![]()
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