Resonance ✏ Chemistry In a Nutshell

Rucete ✏ Chemistry In a Nutshell 

1. What is Resonance?

• Resonance occurs when a molecule or ion can be represented by more than one valid Lewis structure.
• The actual structure is a hybrid of these possible structures.
• Example: Benzene (C₆H₆)
• Carbon-carbon single bonds (0.154 nm) and double bonds (0.134 nm) should have different lengths.
• However, all bond lengths in benzene measure 0.140 nm, indicating delocalized electrons.
• This means benzene does not alternate between single and double bonds but instead has "1.5 bonds"throughout.

2. Why Does Resonance Occur?

• Electron delocalization lowers the molecule’s energy and makes it more stable.
• True structure is a resonance hybrid, not any single resonance form.

3. Common Examples of Resonance

• Benzene (C₆H₆) – Delocalized π electrons create stability.
• Nitrite ion (NO₂⁻) – Two possible structures contribute to the actual form.
• Carbonate ion (CO₃²⁻) – Three equal resonance structures.

In a nutshell

1. Resonance lowers energy and increases stability.
2. Bond lengths in resonance structures are equal (not strictly single or double).
3. Electron delocalization spreads charge over multiple atoms.

"Resonance Relieves Reactivity!"

• Delocalized electrons stabilize molecules.
• Bond lengths become equal (not purely single or double).
• More resonance = More stability.