Thread: Problems with Born-Haber cycles

ok so Born haber cycles assume that all ions are perfect spheres and so all bonding is purely ionic.
But because of the polarisation power of some ions you get some covalent bonding.

Large polarity is with a small densely charged cation. and an anion

Just wondering the best conditions for an anion
if you look at period 3. Chloride ion Cl-)is small with a low charge
Phosphorus ion (P3-) is large with a high charge.

thing is the charge density of each is increased and decreased due to the two factors of charge and size.

which anion causes the most polarisation and why?

thanks to anyone who answers