CARBON
Carbon is first member if group 14 of the periodic table. It has the ground state electronic configuration, [He]2s22p2. It is a typical non-metal forming covalent bonds in a large variety of its compounds by making use of all its valance electrons.
Terrestrial abundance and distribution
Carbon is one of the most widely distributed elements. It occurs in free as well as in the combined states. Free carbon occurs as diamond, graphite and coal. In the combined state, carbon is found as carbonates of calcium, magnesium and other electropositive elements in many minerals. It is sixteenth in the order of abundance in the earth’s crust in many minerals. It also occurs as hydrocarbons in natural gas, petroleum, coal tar etc. In air, carbon in present as carbon dioxide in small quantities but it is very important constituent if atmosphere. CO2 plays very vital role in carbon cycle with photosynthesis and respiration. All living systems contain carbon compounds such as proteins, carbohydrates and fats. The chemistry of carbon has two aspects: inorganic and organic.
Naturally occurring carbon contains two stable isotopes 12C (98.9%) and 13C (1.1%) and traces of radioactive 14C isotope. The isotope 14C has a half life of 5770 years and is used in radio carbon dating for determining the age of archeological specimens of organic origin. The isotope 12C is fixed as an internal standard for measurement of atomic masses and has been assigned a mass of 12.0 units.