Lithium only forms monoxide when heated in oxygen. Sodium forms monoxide and peroxide in excess of oxygen. Other alkali metals form superoxide metals superoxide with oxygen i.e., `MO_(2)`. The abnormal behaviour of lithium is due to small size. The larger size of higher metals also decides the role in formation of superoxide. All the three anions abstract proton from water. The three anions are raleted to each other as follows:
`underset("oxide ion")(O_(2)^(2-)overset((1)/(2)O_(2))(to)underset("peroxide ion")(O_(2)^(2-))overset(O_(2))(to)underset("superoxide ion")(2O_(2)^(-))`
Q. Which anion is stable towards water:

Options

A. `O^(2-)`
B. `O_(2)^(2-)`
C. `O_(2)^(-)`
D. None of these

Explanation

To solve the question regarding the stability of anions towards water, we need to analyze the behavior of the three anions: oxide ion (O²⁻), peroxide ion (O₂²⁻), and superoxide ion (O₂⁻).

### Step-by-Step Solution:

1. **Understanding the Anions**:
- **Oxide Ion (O²⁻)**: This ion is formed when oxygen gains two electrons. It is a strong base and reacts vigorously with water.
- **Peroxide Ion (O₂²⁻)**: This ion consists of two oxygen atoms bonded together with an overall charge of -2. It can also react with water.
- **Superoxide Ion (O₂⁻)**: This ion contains a superoxide bond and has a -1 charge. It is less stable than the oxide and peroxide ions in water.

2. **Reactivity with Water**:
- All three anions (oxide, peroxide, and superoxide) are known to react with water.
- When these anions come into contact with water, they can abstract protons (H⁺ ions) from water, leading to the formation of hydroxide ions (OH⁻) and other products.

3. **Stability Analysis**:
- Since all three anions abstract protons from water, this indicates that they are not stable in aqueous solutions.
- The oxide ion reacts to form hydroxide ions, the peroxide ion can lead to the formation of hydrogen peroxide (H₂O₂), and the superoxide ion can form superoxide radicals.

4. **Conclusion**:
- Given that all three anions are unstable in water and they react with it, the correct answer to the question "Which anion is stable towards water?" is **none of these**.

### Final Answer:
- The correct option is **4. None of these**.