On combustion in excess of air sodium mainly forms `:`

Options

A. `Na_(2)O`
B. `Na_(2)O_(2)`
C. `NaO_(3)`
D. none

Explanation

To solve the question "On combustion in excess of air sodium mainly forms:", we need to analyze the combustion reaction of sodium in the presence of air (which contains oxygen).

### Step-by-Step Solution:

1. **Understanding Combustion of Sodium**:
- Sodium (Na) is a highly reactive alkali metal. When it burns in the presence of oxygen, it forms sodium oxides.

2. **Combustion in Limited Air**:
- In limited air (or limited oxygen), sodium reacts with oxygen to form sodium oxide (Na2O).
- The reaction can be represented as:
\[ 4 \text{Na} + \text{O}_2 \rightarrow 2 \text{Na}_2\text{O} \]

3. **Combustion in Excess Air**:
- When sodium is combusted in excess air (more oxygen is available), it can further react with the oxygen to form sodium peroxide (Na2O2).
- The reaction can be represented as:
\[ 2 \text{Na}_2\text{O} + \text{O}_2 \rightarrow 2 \text{Na}_2\text{O}_2 \]

4. **Stability of Products**:
- Sodium peroxide (Na2O2) is more stable than sodium oxide (Na2O) in the presence of excess oxygen. Therefore, when sodium is burned in excess air, the predominant product formed is sodium peroxide.

5. **Conclusion**:
- Thus, the main product formed when sodium combusts in excess air is sodium peroxide (Na2O2).

### Final Answer:
On combustion in excess of air, sodium mainly forms **sodium peroxide (Na2O2)**.