Which of the following pairs are isostructural ?

Options

A. `XeF_(2), IF_(2)^(-)`
B. `NH_(3), BF_(3)`
C. `CO_(3)^(-2), SO_(3)^(-2)`
D. `PCl_(5), lCl_(5)`

Answer

To determine which pairs of compounds are isostructural, we need to analyze the molecular geometry and hybridization of each compound in the given pairs. Isostructural compounds have the same shape or geometry.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We have the following pairs to analyze:
- Pair 1: Xenon F2 (XeF2) and Iodine F2- (IF2-)
- Pair 2: Ammonia (NH3) and Boron Trifluoride (BF3)
- Pair 3: Carbonate ion (CO3^2-) and Sulfite ion (SO3^2-)
- Pair 4: Phosphorus Pentachloride (PCl5) and Iodine Pentachloride (ICl5)

2. **Analyze Pair 1: XeF2 and IF2-**
- **XeF2**:
- Valence electrons: Xe (8) + 2 (F) = 10
- Hybridization: (8 + 2) / 2 = 5 → sp3d
- Shape: Linear (2 bond pairs, 3 lone pairs)
- **IF2-**:
- Valence electrons: I (7) + 2 (F) + 1 (negative charge) = 10
- Hybridization: (7 + 2 + 1) / 2 = 5 → sp3d
- Shape: Linear (2 bond pairs, 3 lone pairs)
- **Conclusion**: Both are linear, so they are isostructural.

3. **Analyze Pair 2: NH3 and BF3**
- **NH3**:
- Valence electrons: N (5) + 3 (H) = 8
- Hybridization: (5 + 3) / 2 = 4 → sp3
- Shape: Trigonal pyramidal (3 bond pairs, 1 lone pair)
- **BF3**:
- Valence electrons: B (3) + 3 (F) = 6
- Hybridization: (3 + 3) / 2 = 3 → sp2
- Shape: Trigonal planar (3 bond pairs, 0 lone pairs)
- **Conclusion**: Different shapes, so they are not isostructural.

4. **Analyze Pair 3: CO3^2- and SO3^2-**
- **CO3^2-**:
- Valence electrons: C (4) + 3 (O) + 2 (negative charge) = 9
- Hybridization: (4 + 3 + 2) / 2 = 4.5 → sp2
- Shape: Trigonal planar (3 bond pairs, 0 lone pairs)
- **SO3^2-**:
- Valence electrons: S (6) + 3 (O) + 2 (negative charge) = 11
- Hybridization: (6 + 3 + 2) / 2 = 5.5 → sp3
- Shape: Trigonal pyramidal (3 bond pairs, 1 lone pair)
- **Conclusion**: Different shapes, so they are not isostructural.

5. **Analyze Pair 4: PCl5 and ICl5**
- **PCl5**:
- Valence electrons: P (5) + 5 (Cl) = 10
- Hybridization: (5 + 5) / 2 = 5 → sp3d
- Shape: Trigonal bipyramidal (5 bond pairs, 0 lone pairs)
- **ICl5**:
- Valence electrons: I (7) + 5 (Cl) = 12
- Hybridization: (7 + 5) / 2 = 6 → sp3d2
- Shape: Square pyramidal (5 bond pairs, 1 lone pair)
- **Conclusion**: Different shapes, so they are not isostructural.

### Final Conclusion:
The only pair that is isostructural is **Xenon F2 (XeF2) and Iodine F2- (IF2-)**.