A `pi`-molecular orbital is formed by the ............ overlapping of atomic orbitals.

Explanation

To answer the question, "A `pi`-molecular orbital is formed by the ............ overlapping of atomic orbitals," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Molecular Orbitals**:
- Molecular orbitals are formed when atomic orbitals combine. The type of overlap between these orbitals determines the kind of molecular orbital formed.

2. **Types of Overlapping**:
...