Chemistry - Complete s-block Question with Solution | TestHub

The melting and boiling points of alkali metal halides (MX) are primarily determined by lattice energy. Lattice energy is inversely proportional to the internuclear distance (sum of ionic radii). As we go down the halogen group (F to I), the ionic radius increases, leading to a decrease in lattice energy. Therefore, the order of melting/boiling points is $\mathrm{MF}>\mathrm{MCl}>\mathrm{MBr}>\mathrm{MI}$.