Which of the following orbitals of a diatomic molecule AB will not have positive overlap ?

Options

A. 2s(A) and 2s(B)
B. 2s(A) and `2P_z(B)`
C. `2P_z(A) and 2P_z(B)`
D. `2P_x(A) and 2P_z(B)`

Answer

To determine which orbitals of a diatomic molecule AB will not have positive overlap, we need to analyze the types of orbitals involved and their orientations. Here’s a step-by-step solution:

### Step 1: Understand the Concept of Positive Overlap
Positive overlap occurs when two atomic orbitals combine in such a way that their wave functions reinforce each other, leading to a stable bond. This typically happens when orbitals are aligned along the same axis.

### Step 2: Identify the Orbitals
We have the following orbitals to consider:
- 2s of A
- 2s of B
- 2pz of B
- 2px of A
- 2pz of A
- 2pz of B

### Step 3: Analyze Each Pair of Orbitals
1. **2s of A and 2s of B**:
- Both are spherical and can overlap positively along the inter-nuclear axis (z-axis).
- **Result**: Positive overlap.

2. **2s of A and 2pz of B**:
- The 2s orbital is spherical, while the 2pz orbital is oriented along the z-axis.
- They can overlap positively as well.
- **Result**: Positive overlap.

3. **2pz of A and 2pz of B**:
- Both are oriented along the z-axis and can overlap positively.
- **Result**: Positive overlap.

4. **2px of A and 2pz of B**:
- The 2px orbital is oriented along the x-axis, while the 2pz orbital is along the z-axis.
- There is no direct overlap since they are perpendicular to each other, leading to destructive interference.
- **Result**: No positive overlap.

### Step 4: Conclusion
After analyzing all the pairs, the only pair that does not have positive overlap is **2px of A and 2pz of B**.

### Final Answer
The orbitals of a diatomic molecule AB that will not have positive overlap are **2px of A and 2pz of B**.

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