Which of the following has `p pi - d pi ` bonding ?

Options

A. `NO_(3)^(-)`
B. `SO_(3)^(2-)`
C. `BO_(3)^(3-)`
D. `CO_(3)^(2-)`.

Answer

To determine which of the given compounds exhibits p pi - d pi bonding, we need to analyze the options based on the presence of d orbitals and the nature of bonding between the elements involved.

### Step-by-Step Solution:

1. **Understanding p pi - d pi Bonding**:
- p pi - d pi bonding occurs when there is overlap between p orbitals of one atom and d orbitals of another atom. This type of bonding is typically observed when one of the atoms has available d orbitals, which are present in elements from the third period onwards in the periodic table.

2. **Analyzing the Options**:
- **Option A: NO3- (Nitrate Ion)**:
- Nitrogen (N) and Oxygen (O) are both second-period elements. They do not have d orbitals available for bonding. Therefore, p pi - d pi bonding cannot occur here.

- **Option B: SO3- (Sulfite Ion)**:
- Sulfur (S) is a third-period element and has d orbitals available. Oxygen (O) is still a second-period element. In this case, sulfur can utilize its d orbitals to form p pi - d pi bonds with the p orbitals of oxygen.

- **Option C: BO3- (Boron Trioxide)**:
- Boron (B) and Oxygen (O) are both second-period elements, so they lack d orbitals. Hence, p pi - d pi bonding cannot occur here.

- **Option D: CO3 2- (Carbonate Ion)**:
- Carbon (C) and Oxygen (O) are also second-period elements. Therefore, p pi - d pi bonding is not possible in this case as well.

3. **Conclusion**:
- Based on the analysis, the only option that allows for p pi - d pi bonding is **Option B: SO3-**. This is because sulfur can utilize its d orbitals to form bonds with the p orbitals of oxygen.

### Final Answer:
**The compound that exhibits p pi - d pi bonding is SO3-.**