Which of the following set of overlap can not provide `pi` -bond formation

Options

A. (a)3 d and 2p
B. (b)2p and 3p
C. (c)2p and 2p
D. (d)3p and 1s

Answer

To determine which set of overlaps cannot provide π-bond formation, we need to understand the nature of σ and π bonds and the types of orbital overlaps that lead to their formation.

### Step-by-Step Solution:

1. **Understand the Types of Bonds**:
- **Sigma (σ) Bonds**: Formed by head-on (end-to-end) overlapping of orbitals. This can occur between:
- s-s orbitals
- s-p orbitals
- p-p orbitals (along the axis)
- **Pi (π) Bonds**: Formed by sideways (lateral) overlapping of orbitals. This typically occurs between:
- p-p orbitals
- d-d orbitals (in some cases)

2. **Identify Orbital Overlaps**:
- We are given different sets of orbitals and need to identify which set cannot form a π bond.
- π bonds require p orbitals to overlap sideways, so any overlap involving s orbitals cannot form a π bond.

3. **Analyze the Given Options**:
- Check each option for the presence of s orbitals:
- **Option A**: Contains p orbitals only (can form π bonds).
- **Option B**: Contains d orbitals (can form π bonds).
- **Option C**: Contains p orbitals (can form π bonds).
- **Option D**: Contains both 2p and 1s orbitals (cannot form π bonds because of the presence of the s orbital).

4. **Conclusion**:
- The set of overlaps that cannot provide π-bond formation is the one that includes an s orbital. Therefore, the correct answer is **Option D (2p and 1s)**.

### Final Answer:
The set of overlap that cannot provide π-bond formation is **Option D (2p and 1s)**.