ABSTRACT
Ionic solids comprise lattices of positively and negatively charged ions (see 8.2). However, we cannot mix any positively and negatively charged ions and get an ionic solid. Some will simply not combine. One explanation for this is that different ions have different sizes. For a lattice to be stable, the oppositely charged ions must be as close as possible without forcing the like-charged ions into close contact. Some combinations of ion sizes make this impossible.
