Answer:-
Explanations:- Lattice energy depends on two factors, charge and size.
High charge and small size gives higher lattice energy where as low charge and bigger size gives lower lattice energy.
in LiCl, NaCl and KCl, the anion is same and also the charges for Li, Na and K are also same. The deciding factor here is the size of cations. Since the size increases as we move down a group, the order of size of these three atoms is Li<Na<K.
The order of lattice energy is exactly opposite as it's increases as the size decreases.
Now, if we look at magnesium chloride and strontium chloride then again the anion is common but the metals have higher charge as compared to the alkali metals(Li, Na and K). So, lattice energy values must be higher for these two compounds. If we compare Mg and Sr then size of Mg is smaller and so the lattice energy would be greater for this.
Hence, the increasing order of lattice energy is .