Expanded octet structures also become more understandable in light of hybrid orbital theory. The important limitation in the application of the model to molecules is that the "mixing" of orbitals can only occur within a single valence level.

Although hybrid orbital theory pre-dates VSEPR it can successfully explain just about all cases and in fact goes much farther than the more recent model. There is a lot of quantum mechanics and mathematics hiding behind this simple presentation (as you might expect where orbitals are concerned).

Nonetheless, there is a correspondence between the two models and indeed the type of hybrid orbital expected in many molecules can be determined simply by looking at a correctly drawn Lewis structure. Taking the same point of departure as VSEPR, namely the number of electron pairs of any sort on the central atom, this simple approach to determining hybrid orbitals bypasses the orbital diagrams completely but yields essentially the same result. Double and triple bonds are once again treated as single bonds.