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Carbon is an element found in various substances and compounds. Its properties include an atomic number of 6, different allotropes (graphite, diamond, and buckminsterfullerene), and the predictable decay of carbon-14, useful in radiocarbon dating.
Carbon is an element. It is found in bulk, both on its own, in its allotropes, and as a constituent of other widely occurring substances, including limestone, coal, and petroleum. It occurs in a number of inorganic compounds and in all organic compounds. To understand both how carbon acts and how it interacts with other elements, it is important to understand the properties of carbon.
The symbol for carbon in the periodic table is “C”. It is in period 2, along with lithium, beryllium, boron, nitrogen, oxygen, fluorine, and neon, and in group 4a or group 14, depending on the system, with silicon, germanium, tin, and lead. Properties of carbon include an atomic number of 6 and an atomic mass of 12,011 g.mol-1, a melting point of 6332ºF (3500ºC; 3773K), and a boiling point of 8721ºF (4827ºC; 5100K). Carbon has a rating of 0.5 on the Mohs scale of mineral hardness. In a human weighing about 154 lbs (about 70 kg), the average total mass of carbon is about 35 ¼ lb (about 16 kg).
The fact that it has quite different allotropes, or different manifestations of the same element with different molecular structures, is one of the interesting properties of carbon. Graphite, an allotrope, is used to make “lead” in pencils, as well as in generators and electric motors. A second allotrope of carbon is diamond, and a diamond has an absolute score of 1500 on the Mohs scale of mineral hardness, showing how the properties of carbon can differ greatly. Another allotrope, buckminsterfullerene, discovered in 1985 by American and British researchers, has a shape similar to a geodesic dome designed by engineer R. Buckminster Fuller, hence the name.
Among the properties of carbon, the predictable decay of the carbon-14 isotope has been found to be of particular use in dating biological materials. A living organism incorporates a predictable proportion of carbon-12 to carbon-14, which it receives from the atmosphere. When the organism dies, the new carbon is no longer absorbed and the ratio of carbon-12 to carbon-14 begins to change, with carbon-14 decaying into nitrogen-14. This allows for radiocarbon dating based on the 5730 year half-life of carbon-14. Although various situations, such as carbon contamination from the ground and fluctuating amounts of carbon-12 and carbon-14 in the atmosphere, can throw off the calculations, radiocarbon dating has still proved useful.
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