Aluminium metal is not as reactive as expected. Why ?

Explanation

**Step-by-Step Text Solution:**

1. **Understanding Reactivity Series**:
- The reactivity series is a list that ranks metals based on their reactivity from most reactive to least reactive. Aluminium is placed at the top of this series, which suggests that it should be highly reactive.

2. **Formation of Protective Layer**:
- Although aluminium is at the top of the reactivity series, it does not react as vigorously as expected because it quickly reacts with oxygen in the air to form a thin layer of aluminium oxide (Al2O3) on its surface.

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