Which metal is protected by a layer of its own oxide?

Options

A. Al
B. Ag
C. Au
D. Fe

Explanation

To determine which metal is protected by a layer of its own oxide, we can analyze the properties of the given metals: aluminum, silver, gold, and iron.

### Step-by-Step Solution:

1. **Identify the Metals**: The metals in question are aluminum (Al), silver (Ag), gold (Au), and iron (Fe).

2. **Reactivity of Metals**: Among these metals, aluminum is known to be the most reactive. It readily reacts with oxygen in the air.

3. **Formation of Oxide Layer**: When aluminum reacts with oxygen, it forms aluminum oxide (Al2O3). This oxide layer is stable and adheres strongly to the surface of the aluminum.

4. **Protection Against Corrosion**: The aluminum oxide layer acts as a protective barrier, preventing further oxidation and corrosion of the underlying aluminum metal. This phenomenon is known as passivation.

5. **Chemical Reaction**: The reaction can be represented as follows:
\[ 4Al + 3O_2 \rightarrow 2Al_2O_3 \]
This shows that aluminum reacts with oxygen to form aluminum oxide.

6. **Conclusion**: Based on the above analysis, the metal that is protected by a layer of its own oxide is aluminum.

### Final Answer:
The metal that is protected by a layer of its own oxide is **Aluminum (Option A)**.

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