Resonance

Definition

Resonance describes the phenomenon where a molecule can be represented by two or more valid Lewis structures. These structures, called resonance forms, contribute to the overall hybrid structure of the molecule.

5 Must Know Facts For Your Next Test

1. The actual structure of a molecule is a weighted average of its resonance forms, known as the resonance hybrid.
2. Resonance stabilizes molecules by delocalizing electrons over multiple atoms.
3. Only electrons in pi bonds or lone pairs can participate in resonance; sigma bonds do not move in resonance structures.
4. All resonance forms must follow the octet rule and proper valence for each atom involved.
5. The energy of the resonance hybrid is lower than any individual resonance form, contributing to its stability.

Review Questions

• What is the significance of a resonance hybrid in molecular stability?
• Why can't sigma bonds participate in resonance?
• How does delocalization of electrons affect the energy of a molecule?

Related terms

Formal Charge:

The charge assigned to an atom in a molecule, calculated based on the number of valence electrons minus nonbonding electrons and half of bonding electrons.

Lewis Structure:

A diagram that represents the arrangement of atoms within a molecule and shows how valence electrons are distributed.

Octet Rule:

A chemical rule that states atoms tend to bond in such a way that they have eight electrons in their valence shell, giving them an electron configuration similar to noble gases.