Which of the following molecule does not possess a $\pi$ bond?

Question

Accepted Answer

1. **Analyze $H_2O$ (Water):** The central Oxygen atom is bonded to two Hydrogen atoms via single covalent bonds. Oxygen is $sp^3$ hybridized with two lone pairs and two bond pairs. Single bonds are always **sigma ($\sigma$) bonds**. There are no multiple bonds, hence **no $\pi$ bonds** are present.
2. **Analyze $CO_2$:** Structure is $O=C=O$. Each double bond consists of one $\sigma$ and one $\pi$ bond. Total = 2 $\pi$ bonds.
3. **Analyze $SO_2$:** Structure involves resonance between $O=S-O$ forms. It contains $S=O$ double bond character, implying the presence of a $\pi$ bond.
4. **Analyze $NO_2$:** Structure contains a nitrogen atom double-bonded to an oxygen atom in its resonance hybrid ($O=N-O^{\cdot}$). It possesses a $\pi$ bond.
5. **Conclusion:** Only water ($H_2O$) lacks a $\pi$ bond.

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