The molecule having smallest bond angle is

Options

A. `NCl_(3)`
B. `AsCl_(3)`
C. `SbCl_(3)`
D. `PCl_(3)`

Explanation

To determine the molecule with the smallest bond angle among the nitrogen family compounds, we can analyze the bond angles in different compounds of the elements in Group 15 (the nitrogen family). The elements in question are nitrogen (N), phosphorus (P), arsenic (As), and antimony (Sb), specifically their trichlorides (NCl3, PCl3, AsCl3, and SbCl3).

### Step-by-Step Solution:

1. **Identify the Compounds**:
- The compounds we are considering are NCl3, PCl3, AsCl3, and SbCl3.

2. **Understand the Concept of Bond Angles**:
- Bond angles are influenced by the size of the central atom and the presence of lone pairs. Larger central atoms tend to have smaller bond angles due to decreased repulsion between bonding pairs.

3. **Analyze the Central Atoms**:
- **Nitrogen (N)** in NCl3 has a smaller atomic size compared to phosphorus (P), arsenic (As), and antimony (Sb).
- As we move down the group from N to Sb, the atomic size increases.

4. **Consider the Effect of Lone Pairs**:
- NCl3 has one lone pair on nitrogen, which causes greater repulsion between the bonding pairs, leading to a larger bond angle.
- In contrast, SbCl3 has a larger central atom (Sb) with a more diffused lone pair, resulting in less repulsion between the bonding pairs.

5. **Compare Bond Angles**:
- NCl3 has a bond angle of approximately 107 degrees.
- PCl3 has a bond angle of approximately 100 degrees.
- AsCl3 has a bond angle of approximately 90 degrees.
- SbCl3 has the smallest bond angle due to the larger size of Sb leading to decreased repulsion, resulting in a bond angle of approximately 90 degrees or even less.

6. **Conclusion**:
- The molecule with the smallest bond angle is **SbCl3**.

### Final Answer:
The molecule having the smallest bond angle is **SbCl3**.