In an ionic compound, the size of the ions affects the internuclear distance (the distance between the centers of adjacent ions), which affects lattice energy

Question

Based on ion sizes, arrange these compounds by their expected lattice energy.

Note that many sources define lattice energies as negative values. Please arrange by magnitude and ignore the sign. 

∣∣lattice energy∣∣=absolute value of the lattice e

Greatest I lattice energy l (strongest bonds) to least

CsCl

CsBr

CsF

CsI

Answer 1

Since these are all salts of cesium (Cs), we only need look at the anions and rank them from smallest to largest. Atomic radii decrease going UP within a group (all the anions are in group 17). The order from smallest to largest is F < Cl < Br > I

The rank order for lattice energy will therefore be...

CsF > CsCl > CsBr > CsI