Question

Arrange the following in increasing order of lattice energy:

LiCl, NaCl, KCl, RbCl, CsCl

• A. $CsCl<RbCl<KCl<NaCl<LiCl$
• B. $LiCl<RbCl<KCl<NaCl<CsCl$
• C. $LiCl<NaCl<KCl<RbCl<CsCl$
• D. None of these

Answer 1

The correct option is A $CsCl<RbCl<KCl<NaCl<LiCl$

The energy released during the formation of a solid ionic compound from its constituent gaseous ions or in other words the energy used to decompose the ionic solid into its constituent cation and anion is called lattice energy.

For example, in the formation of sodium chloride from sodium ion and chloride ion in gaseous state, 787.3 kj/mol of energy gets released, which is known as the lattice energy of sodium chloride.

The same amount of energy will be used in the decomposition of this ionic solid into its constituent ions.

Overall as we go down in a group, ionic radius increases and lattice energy decrease. In a period from left to right as the charge on ion increases, lattice increases.

$Latticeenergy\propto \frac{Chargeonion}{Sizeofion}$

So, the correct order of lattice energy is $CsCl<RbCl<KCl<NaCl<LiCl$