strength of ionic bond

Columb's law states that : "The magnitude of the electrostatics force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distances between them."

When the ionic size becomes smaller, the distance between the centres of the two ions also becomes smaller. As a result, according to Columb' law, the electrostatic forces between opposite ions becomes strong. In other words, the ionic bonds become stronger.

As the size of ions are smaller, the inter-nuclear distance of the ionic bond is shorter. Thus the electrostatic attraction between positive and negative ions become stronger, the ionic bond become stronger.

smaller size >> shorter internuclear distance >> stronger electrostatic attraction between two nuclei >> stronger ionic bond.