What orbitals can overlap to form a `sigma`-bond and which orbitals can overlap to form a `pi`-bond?

Explanation

To answer the question regarding the types of orbitals that can overlap to form sigma (σ) and pi (π) bonds, we can break down the explanation into clear steps.

### Step-by-Step Solution:

1. **Understanding Sigma Bonds:**
- Sigma bonds are formed through head-on (or end-to-end) overlap of orbitals. This type of overlap occurs along the internuclear axis, which is the line connecting the nuclei of the two atoms involved in the bond.

2. **Orbitals that can form Sigma Bonds:**
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