Question

The compound which has the highest lattice energy is?

• A. $\mathrm{NaF}$
• B. $\mathrm{NaCI}$
• C. $\mathrm{NaBr}$
• D. $\mathrm{NaI}$

Answer 1

The correct option is A

$\mathrm{NaF}$

The explanation for the correct option:

Option(A):$\mathrm{NaF}$

• Generally, if we go down in a group, the ionic radius increases with the decreasing lattice energy whereas, in a period from left to right as the charge on ion increases, lattice energy increases respectively.
• Lattice is mostly inversely proportional to the size of the ion and hence if we go down the group, the increase in the size of the atom will result in a decrease in the lattice energy.
• Thus, the reason that $\mathrm{NaF}$ has the smallest size corresponds to its highest lattice enthalpy.

The explanation for the incorrect option:

Option(B):$\mathrm{NaCI}$

• The compound $\mathrm{NaCI}$ does not have the highest lattice energy as Chlorine has a comparatively larger size than Fluorine.
• Hence, the given option does not represent the correct concept.

Option(C):$\mathrm{NaBr}$

• The compound $\mathrm{NaBr}$ does not have the highest lattice energy as Bromine has a comparatively larger size than Fluorine.
• Thus, the given option is the incorrect one.

Option(D):$\mathrm{NaI}$

• $\mathrm{NaI}$ has the least lattice energy due to the larger size of Iodine.
• Hence, the given option does not coincide with the correct concept.

Hence, the compound which has the highest lattice energy is $\mathrm{NaF}$, option (A) is the correct answer.