Question

The correct order of lattice energy of $I)$, $II)$ and $III)$ is:

$I)$ $BeC{O}_3$
$II)$ $MgC{O}_3$
$III)$ $CaC{O}_3$

• A. I < II < III
• B. I > II > III
• C. I < III < II
• D. II < I < III

Answer 1

The correct option is B I > II > III

Lattice energy is directly proportional to the product of charges of ions and inversely proportional to the inter nuclear distance. Since the anion is the same in all the cases and the charge of the cation is also the same i.e., +2, the deciding factor is the inter nuclear distance. The size of the cation follows the order: $B{e}^{2+}<M{g}^{2+}<C{a}^{2+}$.
Hence order of lattice energy is I > II > III