Chemistry - Complete s-block Question with Solution | TestHub

For a fixed cation, increasing anion size weakens electrostatic attraction, so the lattice dissociation enthalpy decreases:

$\mathrm{LiF}>\mathrm{LiCl}>\mathrm{LiBr}>\mathrm{LiI}$.

Thus A is correct; B and D reverse the expected size trend.

For the divalent anions, ${\mathrm{O}}^{2-}$ is smaller than ${\mathrm{S}}^{2-}$, so $\mathrm{MgO}>\mathrm{MgS}$ in lattice dissociation enthalpy. C is false.