Resonance stabilization, or delocalization stabilization, occurs when the overall energy of the molecule is lowered compared the localized "resonance structures".
In solid state physics, or even when explaining covalent bond formation, it is stated that delocalization occurs due to a lowering of the kinetic energy, just like the ground state evergy of a particle-in-a-box lowers when the size of the box is increased. This explanation is sometimes brought up to explain delocalization stabilization.
This explanation hold even in a single-particle picture, without considering electron-electron interactions. Of course, a molecule is an ensemble of possibly strongly interacting electrons. Several sources claim that delocalization is due to the lowering of the charge repulsion, lowering the potential energy instead.
Of course, both mechanisms are probably at play. My question is the following : In general, does any of these mechanisms dominate ? If not, what are the factors favoring one or the other ?
I could easily understand that charge repulsion plays an important role for charged species like the nitrate ion, while for conjugated molecules or aromaticity, I wouldn't expect electron-electron interactions to dominate. Is this right ?
