Answer:

To determine the compound with the smallest bond angle, we need to consider the electronic and molecular geometries of each compound. The bond angle is influenced by the repulsion between electron pairs around the central atom.

Explanation:

1. Water (H2O): The central atom, oxygen, has two lone pairs and two bonded pairs. The electron pair repulsion causes the bonded pairs to push the lone pairs closer together, resulting in a bent molecular geometry. The bond angle in water is approximately 104.5° due to the electron pair repulsion.

2. Hydrogen sulfide (H2S): Similar to water, the central atom, sulfur, has two lone pairs and two bonded pairs. The repulsion between the electron pairs leads to a bent molecular geometry. However, the lone pairs in sulfur are larger than in oxygen, causing more repulsion and a slightly smaller bond angle. The bond angle in hydrogen sulfide is approximately 92°.

3. Ammonia (NH3): The central atom, nitrogen, has three lone pairs and one bonded pair. The repulsion between the electron pairs results in a trigonal pyramidal molecular geometry. The bond angle in ammonia is approximately 107°, slightly larger than the bond angle in water.

4. Sulfur dioxide (SO2): The central atom, sulfur, has one lone pair and two bonded pairs. The repulsion between the electron pairs leads to a bent molecular geometry. The lone pair in sulfur dioxide exerts more repulsion than the bonded pairs, causing a smaller bond angle. The bond angle in sulfur dioxide is approximately 119°.

Conclusion:

Among the given compounds, hydrogen sulfide (H2S) has the smallest bond angle with a value of approximately 92°. This is because the lone pairs in sulfur are larger than in oxygen, resulting in stronger repulsion and a smaller bond angle.

Ans is NH3 due to lone pair- bond pair repulsion