Which is not a basic oxide ?

Options

A. Sodium oxide
B. Calcium oxide
C. Silicon oxide
D. Iron oxide

Explanation

To determine which of the given options is not a basic oxide, we need to understand the nature of basic oxides and how they interact with water.

### Step-by-Step Solution:

1. **Understand Basic Oxides**:
- Basic oxides are typically metallic oxides. When they react with water, they form bases (alkalis) that are soluble in water.

2. **Identify Non-Metallic Oxides**:
- Non-metallic oxides, on the other hand, are usually acidic. When mixed with water, they form acids.

3. **Analyze the Options**:
- We have four options: Sodium oxide (Na2O), Calcium oxide (CaO), Silicon oxide (SiO2), and Iron oxide (FeO or Fe2O3).

4. **Evaluate Each Option**:
- **Option A: Sodium oxide (Na2O)**:
- Sodium is a metal. Therefore, Na2O is a basic oxide.
- **Option B: Calcium oxide (CaO)**:
- Calcium is also a metal. Thus, CaO is a basic oxide.
- **Option C: Silicon oxide (SiO2)**:
- Silicon is a metalloid. SiO2 can exhibit both acidic and basic properties but is primarily considered an acidic oxide. Therefore, it is not a basic oxide.
- **Option D: Iron oxide (FeO or Fe2O3)**:
- Iron is a metal. Both FeO and Fe2O3 are basic oxides.

5. **Conclusion**:
- The only option that is not a basic oxide is **C: Silicon oxide (SiO2)**.

### Final Answer:
The oxide that is not a basic oxide is **Silicon oxide (SiO2)**.

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