Although metals form basic oxides, which of the following metals form an amphoteric oxide ?

Options

A. Na
B. Ca
C. Al
D. Cu

Explanation

To determine which metal forms an amphoteric oxide, we need to understand the definitions and characteristics of basic and amphoteric oxides.

### Step-by-Step Solution:

1. **Understand Basic Oxides**:
- Metals typically form basic oxides. Basic oxides react with acids to produce salt and water. For example, when sodium oxide (Na2O) reacts with hydrochloric acid (HCl), it forms sodium chloride (NaCl) and water.

2. **Define Amphoteric Oxides**:
- Amphoteric oxides are those that can react with both acids and bases. This means they can behave like both basic and acidic oxides.

3. **Identify Examples of Amphoteric Oxides**:
- A well-known example of an amphoteric oxide is aluminum oxide (Al2O3).

4. **Reactions of Aluminum Oxide**:
- **With Acid**: When aluminum oxide reacts with hydrochloric acid (HCl), it forms aluminum chloride (AlCl3) and water:
\[ \text{Al}_2\text{O}_3 + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2\text{O} \]
- **With Base**: When aluminum oxide reacts with sodium hydroxide (NaOH), it forms sodium aluminate (NaAlO2) and water:
\[ \text{Al}_2\text{O}_3 + 2\text{NaOH} + 3\text{H}_2\text{O} \rightarrow 2\text{NaAlO}_2 + 2\text{H}_2\text{O} \]

5. **Conclusion**:
- Since aluminum oxide can react with both acids and bases, it is classified as an amphoteric oxide. Therefore, the metal that forms an amphoteric oxide among the options given is **aluminum**.

### Final Answer:
The metal that forms an amphoteric oxide is **Aluminum (Al)**.