Which of the following statements is correct ?

Options

A. The `SO_3` molecule has `2 p pi - d pi` bonds in it
B. Isocyanate ion `(NCO^-)` ion is a bent shaped ion
C. The ethene molecule has a total of eight hybrid orbitals.
D. All phosphorous - chlorine bonds in the `PCI_5` molecule are equal in length.

Answer

To determine which of the given statements is correct, we will analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** Sulphur trioxide molecule has two p-pi d-pi bonds in it.

- **Explanation:** Sulfur trioxide (SO₃) has a central sulfur atom that is sp² hybridized. In SO₃, sulfur forms three sigma bonds with three oxygen atoms using its sp² hybrid orbitals. The remaining p-orbitals of sulfur can overlap with the p-orbitals of oxygen to form pi bonds.
- **Hybridization:** The sulfur atom in SO₃ undergoes sp² hybridization, which allows for the formation of one p-pi bond with one oxygen atom and two p-pi d-pi bonds with the other two oxygen atoms.
- **Conclusion:** This statement is correct.

### Step 2: Analyze the second statement
**Statement:** Isocyanate and CO negative ion is a bent shape.

- **Explanation:** The isocyanate ion (NCO⁻) has a linear structure due to the arrangement of its atoms and the hybridization involved. The carbon atom is bonded to nitrogen and oxygen in a linear fashion.
- **Conclusion:** This statement is incorrect.

### Step 3: Analyze the third statement
**Statement:** Ethene molecule has a total of eight hybrid orbitals.

- **Explanation:** Ethene (C₂H₄) consists of two carbon atoms, each of which is sp² hybridized. Each carbon atom has three sp² hybrid orbitals, leading to a total of 6 hybrid orbitals (3 from each carbon).
- **Conclusion:** This statement is incorrect.

### Step 4: Analyze the fourth statement
**Statement:** All phosphorus-chlorine bonds in PCl₅ molecule are equal.

- **Explanation:** Phosphorus pentachloride (PCl₅) has a trigonal bipyramidal structure due to dsp³ hybridization. In this structure, the axial bonds (the bonds that are aligned vertically) are longer than the equatorial bonds (the bonds that lie in the horizontal plane) due to increased repulsion between the axial bonds.
- **Conclusion:** This statement is incorrect.

### Final Conclusion
After analyzing all the statements, we find that the first statement is the only correct one.

**Correct Answer:** The first statement is correct: Sulphur trioxide molecule has two p-pi d-pi bonds in it.

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