Which of the following set of species are isostructural?

Options

A. `overset(+)CH_(3),CH_(3)^(-),NH_(3)`
B. `XeF_(2),BeCl_(2),NO_(2)^(+)`
C. `NH_(3),NH_(4)^(+),CH_(4)`
D. `SF_(4),SiF_(4),XeF_(4)`

Explanation

To determine which set of species are isostructural, we need to analyze the molecular geometry of each species in the given options. Isostructural species have the same shape and geometry. Let's go through the options step by step.

### Step 1: Analyze Option A (CH3+, CH3-, NH3)

1. **CH3+**:
- Central atom: Carbon (C)
- Valence electrons: 4 (C) - 1 (due to +1 charge) = 3
- Bonds: 3 sigma bonds (with H)
- Lone pairs: 0
- **Steric Number**: 3 (3 sigma bonds + 0 lone pairs)
- **Hybridization**: sp²
- **Geometry**: Trigonal planar
- **Shape**: Trigonal planar

2. **CH3-**:
- Central atom: Carbon (C)
- Valence electrons: 4 (C) + 1 (due to -1 charge) = 5
- Bonds: 3 sigma bonds (with H)
- Lone pairs: 1
- **Steric Number**: 4 (3 sigma bonds + 1 lone pair)
- **Hybridization**: sp³
- **Geometry**: Tetrahedral
- **Shape**: Trigonal pyramidal

3. **NH3**:
- Central atom: Nitrogen (N)
- Valence electrons: 5 (N)
- Bonds: 3 sigma bonds (with H)
- Lone pairs: 1
- **Steric Number**: 4 (3 sigma bonds + 1 lone pair)
- **Hybridization**: sp³
- **Geometry**: Tetrahedral
- **Shape**: Trigonal pyramidal

**Conclusion for Option A**: CH3+ is trigonal planar, while CH3- and NH3 are trigonal pyramidal. Therefore, they are not isostructural.

### Step 2: Analyze Option B (XeF2, BeCl2, NO2+)

1. **XeF2**:
- Central atom: Xenon (Xe)
- Valence electrons: 8 (Xe)
- Bonds: 2 sigma bonds (with F)
- Lone pairs: 3
- **Steric Number**: 5 (2 sigma bonds + 3 lone pairs)
- **Hybridization**: sp³d
- **Geometry**: Trigonal bipyramidal
- **Shape**: Linear (due to lone pairs in equatorial positions)

2. **BeCl2**:
- Central atom: Beryllium (Be)
- Valence electrons: 2 (Be)
- Bonds: 2 sigma bonds (with Cl)
- Lone pairs: 0
- **Steric Number**: 2 (2 sigma bonds + 0 lone pairs)
- **Hybridization**: sp
- **Geometry**: Linear
- **Shape**: Linear

3. **NO2+**:
- Central atom: Nitrogen (N)
- Valence electrons: 5 (N) - 1 (due to +1 charge) = 4
- Bonds: 1 sigma bond (with O) + 1 coordinate bond (with O)
- Lone pairs: 0
- **Steric Number**: 2 (2 sigma bonds + 0 lone pairs)
- **Hybridization**: sp
- **Geometry**: Linear
- **Shape**: Linear

**Conclusion for Option B**: All three species (XeF2, BeCl2, NO2+) have a linear shape. Therefore, they are isostructural.

### Step 3: Analyze Option C (NH3, NH4+, CH4)

1. **NH3**:
- Steric Number: 4 (3 sigma bonds + 1 lone pair)
- Shape: Trigonal pyramidal

2. **NH4+**:
- Steric Number: 4 (4 sigma bonds + 0 lone pairs)
- Shape: Tetrahedral

3. **CH4**:
- Steric Number: 4 (4 sigma bonds + 0 lone pairs)
- Shape: Tetrahedral

**Conclusion for Option C**: NH3 is trigonal pyramidal, while NH4+ and CH4 are tetrahedral. Therefore, they are not isostructural.

### Step 4: Analyze Option D (SF4, SiF4, XeF4)

1. **SF4**:
- Steric Number: 5 (4 sigma bonds + 1 lone pair)
- Shape: Seesaw

2. **SiF4**:
- Steric Number: 4 (4 sigma bonds + 0 lone pairs)
- Shape: Tetrahedral

3. **XeF4**:
- Steric Number: 6 (4 sigma bonds + 2 lone pairs)
- Shape: Square planar

**Conclusion for Option D**: All three species have different shapes (seesaw, tetrahedral, square planar). Therefore, they are not isostructural.

### Final Answer:
The correct answer is **Option B**: XeF2, BeCl2, and NO2+ are isostructural.