`pi` bond is formed by

Options

A. overlapping of atomic orbitals on the axis of nuclei
B. mutual sharing of pi electron
C. sidewise over lapping of half filled p-orbitals
D. overlapping of s-orbitals with p-orbitlas

Answer

To determine how a pi bond is formed, we will analyze the options provided and understand the concept behind pi bonds.

### Step-by-Step Solution:

1. **Understanding Atomic Orbitals**:
- Atomic orbitals are regions in an atom where there is a high probability of finding electrons. The most relevant orbitals for bonding are the s and p orbitals.

2. **Types of Overlapping**:
- Bonds between atoms can be formed through overlapping of atomic orbitals. There are two main types of overlapping:
- **Head-on Overlap**: This occurs when orbitals overlap along the axis connecting the two nuclei. This type of overlap leads to the formation of a sigma (σ) bond.
- **Sideways Overlap**: This occurs when orbitals overlap beside each other, rather than end-to-end. This type of overlap leads to the formation of a pi (π) bond.

3. **Formation of Sigma Bonds**:
- For example, if two p orbitals (like px and pz) overlap along the internuclear axis, they form a sigma bond. This is not the case for pi bonds.

4. **Formation of Pi Bonds**:
- Pi bonds are specifically formed by the sideways overlapping of half-filled p orbitals. For instance, if two p orbitals (like py) overlap sideways, they create a pi bond. This overlap occurs above and below the internuclear axis.

5. **Conclusion**:
- Therefore, the correct answer is that a pi bond is formed by the sideways overlapping of p orbitals, which is typically represented in option number three.

### Final Answer:
A pi bond is formed by the sideways overlapping of p orbitals.