Resonance

[JTieu_1L]

Why aren't all resonance structures equal?

[Minh-Thy Vo 3D]

Some resonance structures are more stable than others. The stability is determined by the formal charges, so structures with the lowest formal charges would be more stable. The most stable structure is the major contributor.

[Sabina House 2A]

Just to add, elements want to have the same amount of electrons belonging to them as they have valence electrons, so the more atoms that can fulfill this requirement the better the structure. Some atoms are more likely to accept a negative formal charge due to their electronegativity, and some atoms do not want positive charges because they are very electronegative.

[claire ikemiya_2I]

However, there are instances where the resonance structures are equal!

[BKoh_2E]

It is also good to know that resonance structures are indicative of stability because they represent delocalization of electrons. They spread energy over a larger
area rather than keeping it confined to a small area.

[Gabby Magat 3F]

To add another way to understand the concept, resonance structures provide different areas for electrons to go in order for the molecule to become more stable! Because electrons are delocalized/can move freely, the molecule has lower energy and thus is more stable.

[Gustavo_Chavez_1K]

We want the formal charge of the resonance structures to be as close to 0 as possible. So the structure that provides a formal charge closest to 0 will be considered the most stable.

[Muskaan Abdul-Sattar]

Structures with formal charges closest to zero will be the most stable.

[TiffanyBrownfield 2I]

When a molecule has different resonance structures, the only thing that changes is the arrangement of electrons (structure of atoms, # of lone pairs, and overall formal charge remains the same). However, some resonance structures are more stable because the formal charges of the individual atoms are 0 or closer to 0 than the other resonance structures.

[Edward Castro]

The way I think about it is the closer the formal charge is to zero the more stable it can be.

[Mina Tadros 3L]

Certain resonance structures have a more stable formal charge since they are closer to 0. Structures with the least amount of formal charge tend to be the most stable, and thus, they are the resonance structures that contribute the most to the molecular structure.

[Rose_Malki_3G]

This is because different resonance structures may have atoms with higher or lower formal charges. The resonance structure that is most stable is the one with atoms with the lowest magnitude of formal charge.