Question

Lattice energy depends on:

• A. Only on the radius of cation
• B. Only of radius of the anion
• C. Cation to anion radius ratio
• D. Sum of the radii of cation and anion

Answer 1

The correct option is D

Sum of the radii of cation and anion

The explanation of the correct option:

Option (D): Sum of radii of cation and anion

1. The entire amount of energy necessary to break or convert one mole of aqueous ionic compounds into one mole of ions is known as lattice energy.
2. Lattice energy is given by Coulomb's law $=\mathrm{k}\frac{{\mathrm{Q}}_1{\mathrm{Q}}_2}{\mathrm{r}}$ where Q₁ and Q₂ are numerical ion charges, r is the distance between ion centers, and K is constant$=2.13\times {10}^{-19}$.
3. Also, lattice energy can be given by $U=K\left(\frac{1}{r_a+r_c}\right)$ where r_a is the radius of the anion and r_c is the radius of the cation.
4. The entire distance between two ions in an ionic compound is important in determining the molecule's lattice energy. The weaker the ionic link between two ions, the less lattice energy is required to break the binding and release the compound's ions.
5. The larger the magnitude of charge in the ions, the more strongly the ions are attracted to one other, necessitating the use of more lattice energy to break the ionic bond.
6. Hence it is the correct option.

Therefore, option (D) is correct answer.