Resonance
Definition and meaning of Resonance in chemistry.
Resonance is a conceptual method used to describe delocalized electrons within certain molecules or polyatomic ions where the chemical bonding cannot be accurately expressed by one single Lewis structure.
In more detail
When multiple valid Lewis dot structures can be drawn for a single molecule, the actual, physical structure is a weighted average, or resonance hybrid, of all these contributing structures. Resonance significantly stabilizes a molecule by spreading the electron density over a larger spatial area, thereby reducing the overall potential energy of the system, a phenomenon known as resonance energy. It is critical to understand that the individual resonance structures do not physically exist on their own, nor does the molecule rapidly flip back and forth between them; rather, the molecule exists constantly as a single, stable hybrid. The carbon-carbon bonds in a benzene ring, for instance, are all chemically identical and intermediate in length between a standard single and double bond.
Key facts
| Field | Organic Chemistry |
|---|---|
| Purpose | Describes delocalized electrons |
| Result | Increased stability (resonance energy) |
| Example Molecule | O3 (Ozone) |
The ozone molecule (O3) is represented by two major resonance structures where the double bond shifts between the central oxygen and either terminal oxygen, making both bonds chemically equivalent.
Frequently asked questions
Does a molecule oscillate between its resonance structures?
No, a molecule with resonance is always a single, unchanging hybrid structure, not a mixture of shifting forms.
What makes a resonance structure more stable?
Structures with full octets, fewer formal charges, and negative charges on the most electronegative atoms contribute more to the stability of the hybrid.