Resonance occurs when there are multiple valid Lewis structures for a molecule or ion that differ only in the placement of electrons (specifically pi electrons and lone pairs), not in the arrangement of atoms. This delocalization of electrons leads to increased stability.

Why D is correct:

H₂O (water) is a simple molecule with a bent structure. The central oxygen atom is sp³ hybridized and forms two single bonds with hydrogen atoms and has two lone pairs. All bonds are single (σ) bonds, and there are no adjacent pi bonds or lone pairs that can be delocalized. Therefore, H₂O does not exhibit resonance.

Option Analysis:

• A) C₆H₆ (Benzene): Benzene is the classic example of resonance. It has alternating single and double bonds in a cyclic structure, leading to extensive delocalization of pi electrons over the entire ring.
• B) NO₂ (Nitrogen dioxide): NO₂ has an odd number of electrons and exhibits resonance. The unpaired electron and the pi bond can be delocalized between the nitrogen and oxygen atoms.
• C) CO₃²⁻ (Carbonate ion): The carbonate ion has a central carbon atom bonded to three oxygen atoms. It exhibits resonance due to the delocalization of the pi bond and lone pairs among the carbon and oxygen atoms, resulting in three equivalent resonance structures.
• D) H₂O (Water): As explained above, water only has single bonds and no pi bonds or adjacent lone pairs that can participate in resonance.

Correct Answer: (D)