Define the bond length.

Explanation

### Step-by-Step Solution:

1. **Definition of Bond Length**:
Bond length is defined as the equilibrium distance between the nuclei of two bonded atoms in a molecule. It represents the average distance at which the attractive and repulsive forces between the atoms are balanced.

2. **Understanding Bond Length in Context**:
In a molecule, such as Cl₂ (chlorine gas), the bond length can be visualized as the distance between the centers (nuclei) of the two chlorine atoms when they are bonded together.

...