Carbon

Name:
Carbon
Detailed information:
CAS 7440-44-0. C. A nonmetallic element, atomic number 6, aw 12.011, group IVA of the periodic table, normal valence 4, but divalent forms are known (carbenes). Carbon has two stable and four radioactive isotopes. The ¹²C isotope, which comprises 99% of the element, is the standard to which atomic weights of all other elements are referred (i.e., ¹²C = 12.00 exactly). One mole of carbon atoms (6.02 × 10²³) is contained in 12 g of ¹²C. Carbon has two crystalline allotropes (diamond and graphite) and several amorphous allotropes (coal, coke, carbon black, charcoal). Carbon is present in all organic and in a few inorganic compounds (carbon oxides, carbon disulfide, and metallic carbonates such as calcium carbonate). It is the active element in photosynthesis and thus occurs in all plant and animal life. The radioisotope ¹⁴C is used in tracer research and chemical dating. Carbon is a strong reducing agent and is used as such in purifying metals. It is one of the few elements capable of forming four covalent bonds. Its strong electrical conductivity is used to advantage in electrodes and other electrical devices. Its presence in small proportions in steel has a pronounced effect on the properties of the metal. Carbon forms binary compounds called carbides with many metals and some nonmetals. A few compounds are known that contain divalent carbon (carbenes or methylenes).Since its major properties and uses vary widely with its form, the following entries should be consulted: diamond, graphite, activated carbon, carbon black, industrial carbon, charcoal, wood, coke, steel, carbon cycle.