Carbon is an important non-metallic element. It is the sixth most abundant element in the universe. It can exist in the free state or in the form of its compounds. It is the major chemical constituent of most organic matter. Carbon is the second most common element in the human body after oxygen. Carbon is present in coal, oil and natural gas.
Main natural sources of carbon and its compound which are industrially important are coal, petroleum and natural gas which contribute to our national economy in a big way. Carbon also occurs in a numbers of minerals.
Carbon atoms can form compounds by combining with other carbon atoms as well as atoms of other elements. Carbon has the unique property of forming long chains of carbon atoms. These long chains serve as a backbone on which various groups can attach to give a large variety of compounds. These compounds have a variety of structures, properties and uses in our life.
Carbon belongs to Group 14 of the periodic table. Carbon is abundant in the universe i.e. in Sun, planets, and atmosphere of the Earth. It is present in carbonate rocks - limestone, dolomite, marble. It is also a major constituent of fossil fuels such as coal, petroleum and natural gas. It is present in the form of its compounds in all living organisms. Some such compounds are carbohydrates, proteins, fats. In combination with oxygen, it occurs as carbon monoxide and carbon dioxide. The atmosphere also contains some pollutants arising from these carbon compounds.
In the structure of a carbon atom, there are 4 electrons in the second shell. The electronic configuration of carbon is 2,4. To complete its octet, carbon requires four more electrons. But due to unfavorable energy considerations, it cannot gain four electrons by ion formation and hence attain the electronic configuration of neon. Due to the same reason, it is also not possible for carbon to lose these four electrons and attain the noble gas configuration of helium. However, it can form covalent bonds by sharing these four electrons.
There are three naturally occurring isotopes of carbon - 12C, 13C, 14C. The 14C is a radioactive and its half life is 5730 years. It is used in radio carbon-dating to determine the age of formerly living things.
Carbon can form four covalent bonds. It is tetravalent in nature. It has a valency of four which is according to the rule that Group 14 - 10 = 4. The sharing of four more electrons from other atoms completes the octet of carbon atom and it attains the stability by forming four covalent bonds.
Carbon can form bonds with atoms of other elements such as hydrogen (H), nitrogen (N), oxygen (O), sulphur (S) and halogens (X). It also has the property of self combination i.e. bond formation with the other carbon atoms. Thus, carbon can form long chains of carbon atoms. This unique property of forming long chains is known as catenation.
The carbon-carbon covalent bond is strong in nature. The long carbon chains can act as a backbone to which various groups can attach and give a large number of compounds. The total number of compounds formed by carbon exceeds the total number of compounds formed by all other elements of the periodic table.
In addition to the single covalent bonds, carbon can also form multiple bonds - double or triple bonds with other carbon, oxygen or nitrogen atoms to give a large variety of compounds. The number of compounds formed is so large that a separate branch of chemistry, called organic chemistry, is devoted to the study of these compounds.