Among the following species, the least angle around the central atom is in :

Options

A. `O_(3)`
B. `I_(3)^(-)`
C. `NO_(2)^(-)`
D. `PH_(3)`

Answer

To determine which species has the least bond angle around the central atom, we will analyze the given species: O3 (ozone), I3^- (triiodide ion), NO2^- (nitrite ion), and PH3 (phosphine).

### Step-by-Step Solution:

1. **Analyze O3 (Ozone)**:
- Structure: O3 has a bent shape due to the presence of a lone pair on the central oxygen atom.
- Bond pairs: 2
- Lone pairs: 1
- Hybridization: sp²
- Expected bond angle: Approximately 120°, but due to lone pair repulsion, the actual bond angle is around 116.8°.

2. **Analyze I3^- (Triiodide Ion)**:
- Structure: I3^- has a linear shape.
- Bond pairs: 2
- Lone pairs: 3
- Hybridization: sp³d
- Bond angle: 180° (linear geometry).

3. **Analyze NO2^- (Nitrite Ion)**:
- Structure: NO2^- has a bent shape.
- Bond pairs: 2
- Lone pairs: 1
- Hybridization: sp²
- Expected bond angle: Approximately 120°, but lone pair repulsion may slightly reduce this.

4. **Analyze PH3 (Phosphine)**:
- Structure: PH3 has a trigonal pyramidal shape due to the presence of a lone pair on phosphorus.
- Bond pairs: 3
- Lone pairs: 1
- Hybridization: sp³
- Expected bond angle: Approximately 109.5°, but due to lone pair repulsion, the bond angle is reduced to around 93.5°.

5. **Compare the Bond Angles**:
- O3: 116.8°
- I3^-: 180°
- NO2^-: Approximately 120°
- PH3: Approximately 93.5°

6. **Conclusion**:
- Among the given species, PH3 has the least bond angle around the central atom, which is approximately 93.5°.

### Final Answer:
The species with the least angle around the central atom is **PH3 (phosphine)**.