Among given species identify the isostructural pairs :

Options

A. `[NF_(3) and BF_(3)]`
B. `[BF_(4)^(-) and NH_(4)^(+)]`
C. `[BCl_(3) and BrCl_(3)]`
D. `[NH_(3) and NO_(3)^(-)]`

Explanation

To identify the isostructural pairs among the given species, we need to analyze the hybridization and molecular geometry of each species. Isostructural species have the same number of bond pairs and lone pairs, leading to similar geometries.

### Step 1: Analyze NF3 and BF3
- **NF3**:
- Nitrogen (N) has 5 valence electrons.
- It forms 3 bond pairs with 3 fluorine (F) atoms and has 1 lone pair.
- Hybridization: \( sp^3 \) (3 bond pairs + 1 lone pair).
- Geometry: Pyramidal.

- **BF3**:
- Boron (B) has 3 valence electrons.
- It forms 3 bond pairs with 3 fluorine atoms and has no lone pairs.
- Hybridization: \( sp^2 \) (3 bond pairs).
- Geometry: Trigonal planar.

**Conclusion**: NF3 and BF3 are not isostructural.

### Step 2: Analyze BF4⁻ and NH4⁺
- **BF4⁻**:
- Boron (B) has 3 valence electrons, and with the additional negative charge, it has 4 electrons.
- It forms 4 bond pairs with 4 fluorine atoms.
- Hybridization: \( sp^3 \) (4 bond pairs).
- Geometry: Tetrahedral.

- **NH4⁺**:
- Nitrogen (N) has 5 valence electrons, and with the positive charge, it has 4 electrons.
- It forms 4 bond pairs with 4 hydrogen atoms.
- Hybridization: \( sp^3 \) (4 bond pairs).
- Geometry: Tetrahedral.

**Conclusion**: BF4⁻ and NH4⁺ are isostructural.

### Step 3: Analyze BCl3 and BrCl3
- **BCl3**:
- Boron (B) has 3 valence electrons.
- It forms 3 bond pairs with 3 chlorine (Cl) atoms and has no lone pairs.
- Hybridization: \( sp^2 \) (3 bond pairs).
- Geometry: Trigonal planar.

- **BrCl3**:
- Bromine (Br) has 7 valence electrons.
- It forms 3 bond pairs with 3 chlorine atoms and has 2 lone pairs.
- Hybridization: \( sp^3d \) (3 bond pairs + 2 lone pairs).
- Geometry: T-shaped.

**Conclusion**: BCl3 and BrCl3 are not isostructural.

### Step 4: Analyze NH3 and NO3⁻
- **NH3**:
- Nitrogen (N) has 5 valence electrons.
- It forms 3 bond pairs with 3 hydrogen atoms and has 1 lone pair.
- Hybridization: \( sp^3 \) (3 bond pairs + 1 lone pair).
- Geometry: Pyramidal.

- **NO3⁻**:
- Nitrogen (N) has 5 valence electrons, and with the negative charge, it has 6 electrons.
- It forms 3 double bond pairs with 3 oxygen atoms and has no lone pairs.
- Hybridization: \( sp^2 \) (3 bond pairs).
- Geometry: Trigonal planar.

**Conclusion**: NH3 and NO3⁻ are not isostructural.

### Final Conclusion
The only isostructural pair among the given species is **BF4⁻ and NH4⁺**.

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