Carbon electronic configuration is 1${{s}^{2}}$2${{s}^{2}}$2${{p}^{2}}$ there are 4 electrons in the outermost orbital. It is not possible to remove 4 electrons from a carbon atom to give it the inert gas electron arrangement. Since carbon atom is very small due to which its outermost electrons are strongly held by the nucleus. So carbon atom can achieve the inert gas electron arrangement only by the sharing of electrons, there¬fore carbon always forms covalent bonds.