Question

Arrange $NaF,Mg{F}_2$ and $Al{F}_3$ in the increasing order of their lattice energies.

• A. $Al{F}_3<NaF<Mg{F}_2$
• B. $NaF<Al{F}_3<Mg{F}_2$
• C. $NaF<Mg{F}_2<Al{F}_3$
• D. $Al{F}_3<Mg{F}_2<NaF$

Answer 1

Answer: (C)

$NaF<Mg{F}_2<Al{F}_3$
Lattice energy is directly proportional to the product of charges on ions.
Here, “$F$” anion is same in all the compounds.

$Na(+1),Mg(+2),Al(+3)$

o, the lattice energy follows the order: $NaF<Mg{F}_2<Al{F}_3$