Identify the molecular shapes and approximate bond angles

We compare the bond angles in the given molecules:

• $H_2O$ ($OH_2$): bent shape
• $H_2S$ ($SH_2$): bent shape
• $NH_3$: trigonal pyramidal
• $SO_2$: bent shape

Use VSEPR theory and known bond angle trends

(A) $H_2O$

Oxygen has 2 bond pairs and 2 lone pairs. Ideal tetrahedral angle is $109.5^\circ$, but lone pair-lone pair and lone pair-bond pair repulsions reduce the angle.

$\angle HOH \approx 104.5^\circ$

(B) $H_2S$

Sulfur also has 2 bond pairs and 2 lone pairs, but sulfur is larger and bonding is closer to unhybridized $p$-orbital bonding, so the angle decreases significantly.

$\angle HSH \approx 92^\circ$

(C) $NH_3$

Nitrogen has 3 bond pairs and 1 lone pair. Trigonal pyramidal shape with angle slightly less than tetrahedral.

$\angle HNH \approx 107^\circ$

(D) $SO_2$

Sulfur has 2 bond pairs and 1 lone pair around the central atom (with trigonal planar electron geometry). The bond angle is slightly less than $120^\circ$.

$\angle OSO \approx 119^\circ$

Compare all bond angles

$NH_3 \approx 107^\circ$ $H_2O \approx 104.5^\circ$ $H_2S \approx 92^\circ$ $SO_2 \approx 119^\circ$

The smallest bond angle is in:

$H_2S$

Correct option

Option B: $SH_2$