Which of the following substances exhibits resonance?

• A. ${\mathrm{CH}}_4$ (methane)
• B. $H_{2}O$ (water)
• C. $O_3$ (ozone)
• D. ${\mathrm{NH}}_3$ (ammonia)

Answer: (C)

Verified step by step guidance

1. Understand the concept of resonance: Resonance occurs when a molecule can be represented by two or more valid Lewis structures (resonance structures) that differ only in the placement of electrons, not atoms. This usually happens in molecules with conjugated pi bonds or lone pairs adjacent to pi bonds.
2. Analyze methane (CH\_4): Methane has only single bonds between carbon and hydrogen atoms, with no pi bonds or lone pairs on the carbon that can delocalize electrons. Therefore, it does not exhibit resonance.
3. Analyze water (H\_2O): Water has lone pairs on oxygen, but no adjacent pi bonds or multiple bonds that allow electron delocalization. Its Lewis structure is fixed, so no resonance occurs.
4. Analyze ozone (O\_3): Ozone has a structure with a central oxygen atom bonded to two other oxygens, and it can be represented by resonance structures where the double bond and single bond positions switch between the oxygens. This delocalization of electrons is a classic example of resonance.
5. Analyze ammonia (NH\_3): Ammonia has a lone pair on nitrogen but only single bonds to hydrogen atoms, with no adjacent pi bonds to allow resonance. Thus, it does not exhibit resonance.