Sodium chloride melts at 8000C whereas aluminium chloride sublimes at 1800C Explain 

Sodium chloride melts at 800⁰C whereas aluminium chloride sublimes at 180⁰C. Explain

Sodium ions have low charge density compared aluminium ions

Thus sodium ions weakly polarize chloride ion forming strong ionic bonds that require very high temperature to break; while aluminium ions strongly polarize chloride ions form weak covalent bonds that require low temperature to break.