In which of the following pairs, the two species are isostructural :

Options

A. `SF_4 and XeF_4`
B. `SO_3^(2-) and NO_3^-`
C. `BF_3 and NF_3`
D. `BrO_3^(-) and XeO_3`

Explanation

To determine which pair of species are isostructural, we need to analyze the molecular geometry and hybridization of each species. Here’s a step-by-step breakdown:

### Step 1: Analyze the first pair (SF4 and XeF4)
- **SF4 (Sulfur Tetrafluoride)**:
- Sulfur has 6 valence electrons. It forms 4 bonds with fluorine (4 bond pairs) and has 1 lone pair.
- Hybridization: \( sp^3d \) (4 bond pairs + 1 lone pair).
- Geometry: Seesaw.

- **XeF4 (Xenon Tetrafluoride)**:
- Xenon has 8 valence electrons. It forms 4 bonds with fluorine (4 bond pairs) and has 2 lone pairs.
- Hybridization: \( sp^3d^2 \) (4 bond pairs + 2 lone pairs).
- Geometry: Square planar.

**Conclusion**: SF4 and XeF4 are not isostructural.

### Step 2: Analyze the second pair (SO3^2- and NO3^-)
- **SO3^2- (Sulfite ion)**:
- Sulfur has 6 valence electrons and gains 2 electrons due to the -2 charge. It forms 3 bonds with oxygen (3 bond pairs) and has 1 lone pair.
- Hybridization: \( sp^3 \) (3 bond pairs + 1 lone pair).
- Geometry: Pyramidal.

- **NO3^- (Nitrate ion)**:
- Nitrogen has 5 valence electrons and gains 1 electron due to the -1 charge. It forms 3 bonds with oxygen (3 bond pairs) and has no lone pairs.
- Hybridization: \( sp^2 \) (3 bond pairs).
- Geometry: Trigonal planar.

**Conclusion**: SO3^2- and NO3^- are not isostructural.

### Step 3: Analyze the third pair (BF3 and NF3)
- **BF3 (Boron Trifluoride)**:
- Boron has 3 valence electrons and forms 3 bonds with fluorine (3 bond pairs).
- Hybridization: \( sp^2 \) (3 bond pairs).
- Geometry: Trigonal planar.

- **NF3 (Nitrogen Trifluoride)**:
- Nitrogen has 5 valence electrons. It forms 3 bonds with fluorine (3 bond pairs) and has 1 lone pair.
- Hybridization: \( sp^3 \) (3 bond pairs + 1 lone pair).
- Geometry: Trigonal pyramidal.

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

### Step 4: Analyze the fourth pair (BrO3^- and XeO3)
- **BrO3^- (Bromate ion)**:
- Bromine has 7 valence electrons and gains 1 electron due to the -1 charge. It forms 3 bonds with oxygen (3 bond pairs) and has 1 lone pair.
- Hybridization: \( sp^3 \) (3 bond pairs + 1 lone pair).
- Geometry: Pyramidal.

- **XeO3 (Xenon Trioxide)**:
- Xenon has 8 valence electrons. It forms 3 bonds with oxygen (3 bond pairs) and has 1 lone pair.
- Hybridization: \( sp^3 \) (3 bond pairs + 1 lone pair).
- Geometry: Pyramidal.

**Conclusion**: BrO3^- and XeO3 are isostructural.

### Final Answer
The pair that is isostructural is **BrO3^- and XeO3**.

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