How does ionic bonding affect the melting point?
Intermolecular forces determine the melting points of compounds.
Ionic bond energies range from 250 to 4000 kJ/mol.
It takes much more energy to separate ions than it does to separate molecules from each other.
Consider the compounds CH₃Cl (50 g/mol)) and NH₄Cl (53 g/mol).
They have about the same molar mass, so they should have about the same melting point.
The melting point of CH₃Cl is -97 °C. The melting point of NH₄Cl is 338 °C.
The difference occurs because NH₄Cl consists of NH₄⁺ ions and Cl⁻ ions.