Question

Which of the following compound has the highest lattice energy?

• A. $MgO$
• B. $NaCl$
• C. $CaO$
• D. $KCl$

Answer 1

The correct option is A $MgO$

Lattice energy depends on two important factors. They are:
1. Charge on the ion
2. Size of the ion

On comparing the four given compounds we can see that, $MgO$ and $CaO$ have higher charges (+2 and -2 on the cations and anions respectively) than $NaCl$ and $KCl$ (+1 and -1 on the cations and anions respectively). Therefore $MgO$ and $CaO$ have higher lattuce energies than $NaCl$ and $KCl$.

Among $MgO$ and $CaO$, we see that the anions are the same in both the compounds but the cations differ. Since the charge on both the ions are the same, the cation with smaller size will have higher lattice energy. $M{g}^{2+}$ ion has a smaller size when compared to $C{a}^{2+}$ ad thus $MgO$ has the highest lattice energy among the given compounds.