Carbon mainly forms covalent bonds because carbon atoms have 4 elections in their outermost shell. So it needs to gain or lose electrons to attain noble gas configuration.
- It could gain four electrons forming C4- C4- anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons.
- It could lose four electrons forming C4+ C4+ cation. But it would require a large amount of energy to remove four electrons from its outermost shell.
Because of these reasons, carbon shares its valence electrons to complete its octed with other atoms to form covalent bonds.
Carbon has 4 electrons in its outermost shell. It cannot lose 4 electrons to form C
4+ cation because very high energy is required to remove 4 electrons leaving behind a carbon cation with 6 protons in this nucleus holding onto just 2 electrons. It also cannot gain 4 electrons to form C
4- anion because it is difficult for 6 protons to hold onto 10 electrons. The type of bonds formed in ionic compounds is ionic or electrovalent bonds and in compounds formed by carbon are covalent bonds.
Since the electrons are shared, there are no charged particles in carbon compounds and hence they are poor conductors of electricity.