Arrange compounds by their expected lattice energy.

Question

Based on ion sizes, arrange these compounds by their expected lattice energy from greatest to least.

I am given: MgF₂, MgCl_2, MgI₂, MgBr₂

Answer 1

In genera;. a compound's lattice energy decreases as the size of its ions increase. We can see that the only difference between these compounds is the size of the halogens. Thus, we can rank them as based on size of the halogen; the larger the size, the lower the lattice energy.

For this, we need to keep in mind that atomic radius increases as we go down a group on the periodic table. Applying this to the halogens, we get that:

Smallest atomic radius-F<Cl<Br<I -Largest atomic radius

Therefore we have:

Greatest lattice energy- MgF2>MgCl2>MgBr2>MgI2 - Least lattice energy