Question

Arrange $CsF,RbF,NaF,KF,$ and $LiF$ in the decreasing order of lattice energy:

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

Answer 1

The correct option is D $LiF>NaF>KF>RbF>CsF$

Lattice energy is inversely proportional to the size of the ions involved. Smaller the size of the ions, greater the lattice energy.
The size of cations increases in the following order:
$L{i}^{+}<N{a}^{+}<K^{+}<R{b}^{+}<C{s}^{+}$
Hence, the lattice energy of the compounds follows the order
$CsF<RbF<KF<NaF<LiF$