Question

What is bond angle O-S-O in $\text{SO}_2$ molecule?

• A. $107^\circ$
• B. $180^\circ$
• C. $90^\circ$
• D. $119.5^\circ$

Hint:

For $\text{sp}^2$ configurations containing a single lone pair (like $\text{SO}_2$ or $\text{O}_3$), the strong repulsion from that lone pair always pinches the bond angle to a value slightly below the clean trigonal planar threshold of $120^\circ$.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
We are required to determine the structural O-S-O bond angle within a sulfur dioxide ($\text{SO}_2$) molecule using valence shell electron pair repulsion (VSEPR) theory.

Step 2: Detailed Explanation:
Let's analyze the geometry of the sulfur dioxide ($\text{SO}_2$) molecule:
1.

Steric Number Calculation: Sulfur serves as the central atom, contributing 6 valence electrons. It uses 4 electrons to build two double bonds with two oxygen atoms, leaving exactly 1 non-bonding lone pair. This gives a steric count of 3 (2 $\sigma$-bonds + 1 lone pair), dictating an $\text{sp}^2$ hybridization system.
2.

Molecular Geometry: An ideal $\text{sp}^2$ hybridized framework forms a perfect trigonal planar geometry possessing a benchmark structural angle of exactly $120^\circ$.
3.

VSEPR Deviations: Because lone pair-bonding pair electron clouds repel each other more strongly than bonding pair-bonding pair clouds, the lone pair on the sulfur atom pushes down on the two S=O arms. This electronic compression forces the ideal $120^\circ$ angle down slightly to approximately $119.5^\circ$, creating a bent or V-shaped profile.

Step 3: Final Answer: The actual adjusted bond angle is $119.5^\circ$, which corresponds directly to option (D).