Explain the adsorption of nitrogen on iron.

Explanation

### Step-by-Step Solution:

1. **Understanding Adsorption**:
- Adsorption is the process where molecules from a gas or liquid adhere to a solid surface. It can be classified into two types: physisorption and chemisorption.

2. **Physisorption of Nitrogen on Iron**:
- At low temperatures, specifically at 83 Kelvin, nitrogen (N₂) molecules are physisorbed on the surface of iron.
- Physisorption involves weak van der Waals forces and does not involve any significant change in the electronic structure of the adsorbate or the adsorbent.
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