Which molecule has trigonal planar geometry ?

Options

A. `IF_3`
B. `PCl_3`
C. `NH_3`
D. `BF_3`

Explanation

To determine which molecule has a trigonal planar geometry, we will analyze the molecular geometry of each given molecule step by step.

### Step 1: Analyze IF3 (Iodine Trifluoride)
- **Valence Electrons**: Iodine (I) has 7 valence electrons. Each fluorine (F) has 7 valence electrons.
- **Bonding**: Iodine forms 3 bonds with 3 fluorine atoms, using 3 of its valence electrons.
- **Lone Pairs**: After forming 3 bonds, iodine has 2 lone pairs remaining.
- **Hybridization**: The hybridization is calculated as the sum of bond pairs and lone pairs:
- Bond pairs = 3
- Lone pairs = 2
- Total = 3 + 2 = 5 → Hybridization = sp³d
- **Geometry**: The molecular shape is T-shaped due to the presence of lone pairs.

### Step 2: Analyze PCl3 (Phosphorus Trichloride)
- **Valence Electrons**: Phosphorus (P) has 5 valence electrons. Each chlorine (Cl) has 7 valence electrons.
- **Bonding**: Phosphorus forms 3 bonds with 3 chlorine atoms.
- **Lone Pairs**: After forming 3 bonds, phosphorus has 1 lone pair remaining.
- **Hybridization**:
- Bond pairs = 3
- Lone pairs = 1
- Total = 3 + 1 = 4 → Hybridization = sp³
- **Geometry**: The molecular shape is trigonal pyramidal due to the lone pair.

### Step 3: Analyze NH3 (Ammonia)
- **Valence Electrons**: Nitrogen (N) has 5 valence electrons. Each hydrogen (H) has 1 valence electron.
- **Bonding**: Nitrogen forms 3 bonds with 3 hydrogen atoms.
- **Lone Pairs**: After forming 3 bonds, nitrogen has 1 lone pair remaining.
- **Hybridization**:
- Bond pairs = 3
- Lone pairs = 1
- Total = 3 + 1 = 4 → Hybridization = sp³
- **Geometry**: The molecular shape is also trigonal pyramidal due to the lone pair.

### Step 4: Analyze BF3 (Boron Trifluoride)
- **Valence Electrons**: Boron (B) has 3 valence electrons. Each fluorine (F) has 7 valence electrons.
- **Bonding**: Boron forms 3 bonds with 3 fluorine atoms.
- **Lone Pairs**: After forming 3 bonds, boron has no lone pairs remaining.
- **Hybridization**:
- Bond pairs = 3
- Lone pairs = 0
- Total = 3 + 0 = 3 → Hybridization = sp²
- **Geometry**: The molecular shape is trigonal planar since there are no lone pairs.

### Conclusion
Among the analyzed molecules, **BF3 (Boron Trifluoride)** has a trigonal planar geometry.