Question

Why ionic compounds have high melting and boiling point?

Answer 1

Ionic compounds are made up of ions, that is, an equal number of cations and anions.

Hence, the electrostatic force of attraction between the cations and the anions is very strong, which results in the formation of the ionic bond.

So, a lot of energy is needed to break the the electrostatic force of attraction between the cations and the anions, resulting in high melting and boiling points.

For example, the melting and boiling point of Sodium chloride $\left(\mathrm{NaCl}\right)$ is $801°\mathrm{C}$ and $1413°\mathrm{C}$.