Which of the following orbital overlapping is not possible according to VBT?

Options

A.
B.
C.
D. All of these

Answer

To determine which orbital overlapping is not possible according to Valence Bond Theory (VBT), we need to analyze the types of overlaps mentioned in the options.

### Step-by-Step Solution:

1. **Understanding Orbital Overlaps**:
- VBT states that certain types of orbital overlaps can form bonds. The two main types of overlaps are sigma (σ) and pi (π) overlaps.
- Sigma bonds are formed by the head-on overlap of orbitals, while pi bonds are formed by the side-to-side overlap of p orbitals.

2. **Identifying the Overlaps**:
- Let's consider the types of overlaps mentioned in the options:
- **s-p overlap**: This is a sigma bond (σ) formed by the overlap of an s orbital and a p orbital.
- **p-p overlap**: This can form either a sigma bond (σ) or a pi bond (π) depending on the orientation of the p orbitals.
- **s-s overlap**: This forms a sigma bond (σ) as well.

3. **Analyzing Each Option**:
- **Option 1**: s orbital and p orbital forming a pi bond (π). According to VBT, this is not possible because s orbitals cannot participate in pi bonding.
- **Option 2**: p orbital and p orbital forming a pi bond (π). This is possible, but if one is sigma and the other is pi, that specific overlap is not allowed.
- **Option 3**: p orbital and p orbital forming a sigma bond (σ). This is possible if they are aligned correctly.

4. **Conclusion**:
- The overlaps that are not possible according to VBT are:
- s-p forming a pi bond (π).
- p-p forming a sigma bond (σ) with opposite polarity.

Thus, the answer to the question is that the overlap of an s orbital with a p orbital to form a pi bond is not possible according to VBT.