The Strength of Ionic Bonds

The strength of an ionic bond depends on the size of the ions and the charge on the ions.Size: The smaller the ions the more energy is required to overcome the electrostatic forces of attraction.Charge: The greater the charge the more energy is required to overcome the electrostatic forces of attraction.
Magnesium oxide has stronger ionic bonds than sodium chloride as the magnesium ion Mg²⁺ and the oxide ion O^2- are doubly charged while the sodium ion Na⁺ and Chloride ion Cl^- have single charge.Lithium chloride has a stronger ionic bond than potassium chloride as the lithium ion is smaller.