Chemistry - Complete s-block Question with Solution | TestHub

The lattice energy of an ionic compound is the energy required to separate one mole of the compound into its constituent ions in the gas phase.

 Lattice energy$\propto \frac{1}{\left(r_{+}+r_{-}\right)}$

The lattice energy is inversely proportional to the sum of the ionic radii $\left({\mathrm{r}}_{+}+{\mathrm{r}}_{-}\right)$ of the ions involved. When the size of the ions increases, the distance between them also increases, leading to a decrease in the attractive forces between the ions and a decrease in the lattice energy. Therefore, if the size of the ions increases, the lattice energy generally decreases.

So Order : $\mathrm{NaF} > \mathrm{NaCl} > \mathrm{NaBr} > \mathrm{NaI}$