Question

State the reason why carbon can neither form $C^{4+}$ cations nor $C^{4-}$ anions but forms covalent compounds. Also, state reasons to explain why covalent compounds:
(i) are bad conductors of electricity?
(ii) have low melting and boiling points?

Answer 1

The atomic number of Carbon is 6 with an electronic configuration of 2, 4. Hence, carbon has 4 electrons in its valence shell. Carbon can lose or gain 4 electrons in order to gain stability. It cannot gain four electrons as carbon atom having 6 protons is very small to handle 10 electrons and it cannot donate electrons as it needs a lot of energy to do so. Hence, it cannot form $C^{4+}$ cation or $C^{4-}$ anion and thus forms a covalent bond.

1. Covalent compounds are formed by sharing of electrons. They don't have a free electron that is required for electricity transfer (electricity is the flow of free electrons), thus they are bad conductors.

2. Covalent compounds have low melting and boiling points because they have weak inter-molecular forces between bonds. Hence, less energy/temperature is needed to break the bonds.