Delocalization of Electron

[Mahnoor_Wani_1I]

While watching today's lecture, I was confused about the concept of delocalization vs localization. Can someone explain to what each terms means in terms of resonance structures. Also, why does the delocalization of electrons increases a molecule or compound stability?

[Ria Nawathe 1C]

Delocalized electrons are electrons that do not "belong" to a particular atom or are not associated with a specific bond in the molecule. Here is the textbook's explanation for why it increases stability (it's in Focus 2B):

"As well as delocalizing electrons over the atoms, resonance also lowers the energy below that of any single contributing structure and helps to stabilize the molecule. This lowering of energy occurs for quantum mechanical reasons. Broadly speaking, the wavefunction that describes the resonance structure is a more accurate description of the electronic structure of the molecule than the wavefunction for any single structure alone, and the more accurate the wavefunction, the lower the corresponding energy."

[Akshata Kapadne 2K]

Normally, electrons are localized, which means that that they remain close to one atom and don't travel to other atoms. They are "fixed', in a way. Most Lewis structures show localized electrons. On the other hand, delocalized electrons move between different atoms, which can be seen through resonance, since electrons move from atom to atom. I believe the delocalization of electrons increases stability by lowering the overall energy by spreading out the electrons, but I'm not completely sure.