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 of the given pairs of compounds are isostructural, we need to analyze their hybridizations and molecular geometries. Isostructural species have the same shape and hybridization.

### Step-by-Step Solution:

1. **Identify the pairs of compounds**:
- Pair 1: XEF2 and IF2-
- Pair 2: NH3 and BF3
- Pair 3: CO3^2- and SO3^2-
- Pair 4: PCl5 and ICl5

2. **Analyze Pair 1: XEF2 and IF2-**:
- **XEF2**: The central atom (Xe) is surrounded by two fluorine atoms and has three lone pairs. The hybridization is sp3, and the molecular geometry is linear due to the arrangement of the lone pairs.
- **IF2-**: The central atom (I) is surrounded by two fluorine atoms and has three lone pairs. The hybridization is also sp3, and the molecular geometry is linear.
- **Conclusion**: Both XEF2 and IF2- are isostructural.

3. **Analyze Pair 2: NH3 and BF3**:
- **NH3**: The central atom (N) is surrounded by three hydrogen atoms and has one lone pair. The hybridization is sp3, and the molecular geometry is tetrahedral.
- **BF3**: The central atom (B) is surrounded by three fluorine atoms and has no lone pairs. The hybridization is sp2, and the molecular geometry is trigonal planar.
- **Conclusion**: NH3 and BF3 are not isostructural.

4. **Analyze Pair 3: CO3^2- and SO3^2-**:
- **CO3^2-**: The central atom (C) is surrounded by three oxygen atoms. The hybridization is sp2, and the molecular geometry is trigonal planar.
- **SO3^2-**: The central atom (S) is surrounded by three oxygen atoms and has one lone pair. The hybridization is sp3, and the molecular geometry is trigonal pyramidal.
- **Conclusion**: CO3^2- and SO3^2- are not isostructural.

5. **Analyze Pair 4: PCl5 and ICl5**:
- **PCl5**: The central atom (P) is surrounded by five chlorine atoms. The hybridization is sp3d, and the molecular geometry is trigonal bipyramidal.
- **ICl5**: The central atom (I) is also surrounded by five chlorine atoms. The hybridization is sp3d2, and the molecular geometry is square pyramidal.
- **Conclusion**: PCl5 and ICl5 are not isostructural.

### Final Conclusion:
The only pair that is isostructural is **XEF2 and IF2-**.