Carbon is one of the most important widely distributed elements on the Earthâ€™s crust. It occurs in nature, both in the free and in the combined states. Carbon compounds are found in all living things.
Carbon is the first member of group IVA of the periodic table. This IVA also includes silicon, germanium, tin and lead. It is placed between the electropositive elements of group IIIA and the electronegative elements of group VA. These elements have four electrons in their outermost orbit, which is why they have valency four. It should lose four electrons or gain four electrons to attain the noble gas configuration. Either gaining four electrons or losing four electrons are difficult for the nucleus. When gaining four electrons the nucleus has to hold extra four electrons and when losing, it would require a large amount of energy to remove four electrons.
To over come this problem, carbon shares its valence electrons with other elements and forms covalent bond. Just like carbon many elements like hydrogen, oxygen, nitrogen, etc. form covalent bonds.