The electronic configuration of carbon is K L / 2 4. Thus, an atom of carbon contains 4 electrons in its outermost shell, i.e., carbon has been 4 valence electrons. To gain stability, it should lose its valence electrons, gain four more electrons or share its 4 valence electrons with other atoms. Carbon atom has been no tendency to lose its four valence electrons or gain four more electrons from other atoms. Therefore, carbon atom completes its octet only by sharing its valence electrons with other atoms. As a result, therefore carbon always forms only covalent bonds with other atoms.