State the reason why carbon can neither form C⁴⁺ cations nor C^4- anions but forms a covalent compound. Also state the reason to explain why covalent compounds: (i) are bad conductors of electricity (ii) have low melting and boiling points.

C⁴⁺ means removing of four electrons from the carbon atom. But, carbon cannot form C⁴⁺ because:

i. Removing four electrons from the valence shell requires an input of a large amount of energy

ii. The successive ionisation energy goes on increasing.

C⁴⁺ means the addition of four electrons in a carbon atom. But, carbon cannot form C^4- because:

i. Addition of four electrons in the valence shell is also not possible because again the successive electron affinity goes on increasing.

ii. But yet, carbon needs four electrons to complete its octet. Thus, the only method available for that is sharing of electrons; in doing so, a covalent bond is formed.

Covalent compounds are bad conductors of electricity because:

i. To conduct electricity, a substance must contain a charged particle.

ii. Covalent bonds are formed by sharing of electrons. Thus, they do not contain any charged particle and are thus bad conductors of electricity.

Covalent compounds have low melting and boiling point because:

i. Covalent compounds are formed as a result of covalent bonding.

ii. The forces present in covalent bonds are held together by weak Vander Waals forces. Or we can say that the force of attraction between these molecules is not very strong.

iii. A supply of a small amount of energy can weaken this force to a great extent that is why carbon compounds have low melting and boiling point.