The atomic number of carbon is 6 which means that a neutral atom of carbon, retains 6 electrons. So the electrons configuration of carbon is K=2, L=4.
Since, carbon has 4 electrons in tis outmost shell so, it should either lose or gain 4 electrons to achieve the inert gas configuration and becomes table.
(i) It could gain four electrons forming `C^(4-)` anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons due to inter electronic repulsion.
(ii) It could lose 4 electrons formign `C^(4+)` cation. But it would require a large amount of energy to remove four electrons from its outermost shell.
Thus, it forms compounds mainly by covalent bonds.
Two properties of carbon which lead to huge number of carbon compounds are `:`
(i) Catenation `:` Catenation is the unique property of carbon atoms to form bonds with other atoms of carbon giving rise to large molecules.
(ii) Tetravelency `:` Since carbon has a valency of 4, it is capable of bonding with 4 other atoms of carbon or atoms of some other monovalent element.
The reason for the formation of strong bonds by the carbon atoms is their small atomic size. Due to the small size of carbon atoms their nuclei hold the shared pairs of electrons between atoms strongly covalent bonds with the atoms of other elements such as hydrogen oxygen, nitrogen , sulphur, chlorine and other elements.