Ionic compounds have high melting points because they consist of closely packed ions held together by strong electrostatic forces of attraction between oppositely charged ions (cations and anions). These strong ionic bonds require a large amount of energy to overcome in order to break the bonds and melt the compound. The ionic lattice structure contains many ions, and the cumulative effect of these strong forces results in high melting and boiling points for ionic compounds.
In summary, the reason ionic compounds have high melting points is that strong ionic bonds formed by electrostatic attraction between ions demand a significant energy input to disrupt the ionic lattice, causing the melting point to be high.
