Which of following statement is correct ? .

Options

A. The bond angle of `NCI_(3)` is greater than that of `NH_(3)`
B. The bond angle of `PH_(3)` is greater than that of `PF_(5)`
C. `CIO_(3)^(Θ)` and `SO_(3)^(2-)` are isostructural
D. It is not necessary that in Tbp structure the lone pairs always would occupy the equatorial positions .

Explanation

To solve the question regarding which of the following statements is correct, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** The bond angle of NCl3 is greater than that of NH3.

1. **Structure of NCl3:** NCl3 has a pyramidal structure. Chlorine is more electronegative than nitrogen, which causes the bond pairs to be pulled closer to the chlorine atoms. This results in decreased bond pair-bond pair repulsion, leading to a smaller bond angle.

2. **Structure of NH3:** NH3 also has a pyramidal structure, but here nitrogen is more electronegative than hydrogen. This causes the bond pairs to be pulled closer to the nitrogen atom, increasing bond pair-bond pair repulsion and resulting in a larger bond angle.

**Conclusion for Statement A:** The bond angle of NCl3 is less than that of NH3. Therefore, Statement A is **false**.

### Step 2: Analyze Statement B
**Statement B:** The bond angle of PH3 is greater than that of PF5.

1. **Structure of PH3:** PH3 has a pyramidal structure with bond angles less than 109.5 degrees due to lone pair-bond pair repulsion.

2. **Structure of PF5:** PF5 has a trigonal bipyramidal structure with bond angles of 90 degrees, 120 degrees, and 180 degrees.

**Conclusion for Statement B:** Since the bond angle in PH3 is less than 109.5 degrees and PF5 has bond angles of 90 degrees and 120 degrees, we cannot directly compare them. However, we can conclude that Statement B is **false**.

### Step 3: Analyze Statement C
**Statement C:** ClO3- and SO3-2 are isostructural.

1. **Valence Electrons in ClO3-:**
- Chlorine (Cl) has 7 valence electrons.
- Each Oxygen (O) has 6 valence electrons, and there are 3 O atoms.
- The negative charge adds 1 electron.
- Total = 7 + (3 × 6) + 1 = 26 valence electrons.

2. **Valence Electrons in SO3-2:**
- Sulfur (S) has 6 valence electrons.
- Each Oxygen (O) has 6 valence electrons, and there are 3 O atoms.
- The 2 negative charges add 2 electrons.
- Total = 6 + (3 × 6) + 2 = 26 valence electrons.

**Conclusion for Statement C:** Both species have the same number of valence electrons (26), making them isostructural. Therefore, Statement C is **true**.

### Step 4: Analyze Statement D
**Statement D:** It is not necessary that in a trigonal bipyramidal structure the lone pairs always occupy the equatorial positions.

1. In a trigonal bipyramidal structure, to minimize lone pair-bond pair and lone pair-lone pair repulsions, lone pairs prefer to occupy equatorial positions.

**Conclusion for Statement D:** This statement is **false** because it is necessary for lone pairs to occupy equatorial positions to minimize repulsions.

### Final Conclusion
The correct statements are:
- Statement C is correct (ClO3- and SO3-2 are isostructural).
- Statement A and B are false.
- Statement D is false.

Thus, the correct answer to the question is **Statement C**.

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