Select correct statement(s) regarding `sigma and pi` bonds :

Options

A. `sigma`-bond lies on the line joining the nuclei of bonded atoms
B. `pi-` electron cloud lies on either side to the line joining the nuclei of bonded atoms
C. `(2ppi-3dpi)pi`-bond is stronger than `(2ppi-2pi)pi`-bond
D. `sigma`-bond has primary effect to decide direction of covalent bond, which `pi-` bond has no primery effect in direction of bond.

Answer

To solve the question regarding the correct statements about sigma (σ) and pi (π) bonds, we will analyze each statement based on the principles of chemical bonding.

### Step-by-Step Solution:

1. **Understanding Sigma Bonds**:
- Sigma bonds are formed by the head-on overlap of atomic orbitals. This can occur between:
- An s orbital and a p orbital (e.g., s-p overlap).
- Two p orbitals (e.g., p-p overlap).
- The overlap occurs along the internuclear axis, which is the line connecting the nuclei of the bonded atoms.

**Hint**: Remember that sigma bonds are the first bonds formed between two atoms and have a cylindrical symmetry around the bond axis.

2. **Understanding Pi Bonds**:
- Pi bonds are formed by the side-to-side overlap of p orbitals. This can occur between:
- Two p orbitals (e.g., p-p overlap).
- Pi bonds exist above and below the plane of the sigma bond, and they can only form after a sigma bond has already been established.

**Hint**: Pi bonds add to the bonding between atoms but do not influence the bond direction like sigma bonds do.

3. **Analyzing the Statements**:
- **Statement 1**: "Sigma bond lies on the line joining the nuclei of the bonded atoms."
- This statement is **correct** because sigma bonds are formed along the internuclear axis.

- **Statement 2**: "Pi electron cloud lies on either side of the line joining the nuclei of the bonded atoms."
- This statement is **correct** because pi bonds have electron density above and below the internuclear axis.

- **Statement 3**: "2pπ 3dπ, Pi bond is stronger than 2pπ, 2pπ bond."
- This statement is **incorrect** because the overlap of 3d orbitals is generally less effective than that of 2p orbitals, making the 2pπ bond stronger than the 3dπ bond.

- **Statement 4**: "Sigma bond has a primary effect to decide the direction of the covalent bond which Pi bond has no primary effect."
- This statement is **correct** because sigma bonds determine the orientation of the bond, while pi bonds do not influence the bond direction.

4. **Conclusion**:
- The correct statements regarding sigma and pi bonds are:
- Statement 1: Correct
- Statement 2: Correct
- Statement 3: Incorrect
- Statement 4: Correct

### Final Answer:
The correct statements are 1, 2, and 4.