Question

The compound that has the highest lattice energy is:

• A. $RbF$
• B. $CsF$
• C. $NaF$
• D. $KF$

Answer 1

The correct option is C $NaF$

Lattice Energy is directly proportional to the product of the charges of ions and inversely proportional to the size of ions (i.e. interionic distance between them).
Since the anion $\left(F^{-}\right)$ is common in all the given compounds, lattice energy order will only depend on the cation. Here, all the given cations belong to same group of the periodic table and they all have the same charge too i.e. $+1$.
Therefore, we can say that the order will be based on the size of cation only i.e. smaller the size of the cation, more will be the lattice energy. Also, on moving down the group size of the atom increases.

Therefore, $N{a}^{+}$ has the smallest size and hence $NaF$ will have the highest lattice energy.