Question

How do we quantify the strength of ionic bonding?

Answer 1

As you know, bonding in sodium chloride is non-molecular. The lattice is held together by electrostatic interaction.

Explanation:

Consider the sodium ion, `Na^+`, in the lattice. It has an electrostatic interaction (an attractive interaction), with its 6 chloride nearest neighbours, with the force of interaction given by Coulomb's law. There is also an electrostatic force of interaction with EVERY other negative ion in the lattice.

Now, of course there is also an electrostatic force of interaction with every other SODIUM ion in the lattice. And, because these are LIKE charges, the force of interaction is REPULSIVE. But if you sum up ALL the attractive forces and repulsive forces of the electrostatic interaction, the attractive force that holds the lattice together wins. Much experimental and theoretical data support and informs this conclusion. Consider Born-Haber cycles. This is a useful site.