1.35 understand the relationship between ionic charge and the melting point and boiling point of an ionic compound

Ionic Compounds

We know that ionic compounds are two ions which are attracted by electrostatic forces. This is because like forces attract. If the charges are increased and each ions have a greater charge then they will have greater electrostatic forces. This means more energy is required to break them so they have a higher melting/boiling point. 

e.g

Mg²⁺O²⁺ has a higher melting point than Na⁺Cl^-