Choose the molecules in which hybridization occurs in the ground state?
(P) `BCl_(3)`
(Q) `NH_(3)`
(R) `PCl_(3)`
(S) `BeF_(2)`

Options

A. P, Q, S
B. P, Q, R
C. Q, R
D. R, S

Explanation

To determine which molecules undergo hybridization in the ground state, we will analyze the electronic configurations and bonding of the given molecules: BCl₃, NH₃, PCl₃, and BeF₂.

### Step-by-Step Solution:

1. **Analyze BCl₃ (Boron Trichloride)**:
- **Electronic Configuration of Boron**:
- Atomic number of Boron (B) is 5.
- Configuration: 1s² 2s² 2p¹.
- **Valence Shell Configuration**:
- Before hybridization: 2s² 2p¹ (only one unpaired electron).
- **Hybridization**:
- To form three bonds with chlorine, one of the 2s electrons must be excited to the 2p orbital, resulting in three unpaired electrons.
- **Conclusion**: Hybridization occurs in the excited state, not the ground state.

2. **Analyze NH₃ (Ammonia)**:
- **Electronic Configuration of Nitrogen**:
- Atomic number of Nitrogen (N) is 7.
- Configuration: 1s² 2s² 2p³.
- **Valence Shell Configuration**:
- Before hybridization: 2s² 2p³ (three unpaired electrons).
- **Hybridization**:
- The three unpaired electrons in the 2p orbitals can bond with three hydrogen atoms without any excitation.
- **Conclusion**: Hybridization occurs in the ground state.

3. **Analyze PCl₃ (Phosphorus Trichloride)**:
- **Electronic Configuration of Phosphorus**:
- Atomic number of Phosphorus (P) is 15.
- Configuration: [Ne] 3s² 3p³.
- **Valence Shell Configuration**:
- Before hybridization: 3s² 3p³ (three unpaired electrons).
- **Hybridization**:
- The three unpaired electrons can bond with three chlorine atoms without any excitation.
- **Conclusion**: Hybridization occurs in the ground state.

4. **Analyze BeF₂ (Beryllium Fluoride)**:
- **Electronic Configuration of Beryllium**:
- Atomic number of Beryllium (Be) is 4.
- Configuration: 1s² 2s².
- **Valence Shell Configuration**:
- Before hybridization: 2s² (no unpaired electrons).
- **Hybridization**:
- To form bonds with two fluorine atoms, one of the 2s electrons must be excited to the 2p orbital, resulting in two unpaired electrons.
- **Conclusion**: Hybridization occurs in the excited state, not the ground state.

### Final Conclusion:
The molecules in which hybridization occurs in the ground state are:
- **NH₃ (Ammonia)**
- **PCl₃ (Phosphorus Trichloride)**

### Answer:
**Q (NH₃) and R (PCl₃)** are the correct answers.