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 energy

arrange from greatest lattice energy (strongest bonds) to least lattice energy (weakest bonds)

SrBr2

BaBr2

BeBr2

MgBr2

CaBr2

Answer 1

Since the anion in all of the salt is Br-, we need only concern ourselves with the size (atomic radius) of the cation. Since all of the cations are in the same group (group 2), and since atomic radius decreases going UP within a group, we can arrange the cations from smallest to largest as follows:

Be < Mg < Ca < Sr < Ba

So, final order of LE from greatest to least would be

BeBr₂ > MgBr₂ > CaBr₂ > SrBr₂ > BaBr₂