Which of the following statements is incorrect ?

Options

A. The superoxide ion `(i.e. O_(2)^(-))` is stable only in presence of larger cations such as `K^(+),Rb^(+),Cs^(+)`
B. Alkali metals are normally kept in kerosene oil.
C. All the alkali metal hydrides are ionic solids with high melting points.
D. The concentrated solution of alkali metals in liquid ammonia is paramagnetic in nature.

Explanation

To determine which of the following statements is incorrect regarding alkali metals and their properties, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Statement 1: Superoxide ion (O2-) is stable only in the presence of larger cations such as K+, Rb+, Cs+.**
- The superoxide ion (O2-) is indeed a larger anion. It forms stable complexes with larger cations due to the size compatibility. Larger cations like K+, Rb+, and Cs+ can stabilize the larger anion effectively.
- **Conclusion:** This statement is **correct**.

2. **Statement 2: Alkali metals are normally kept in kerosene oil.**
- Alkali metals are highly reactive, especially with water and air. To prevent reactions, they are stored in kerosene oil, which acts as a protective medium.
- **Conclusion:** This statement is **correct**.

3. **Statement 3: All alkali metal hydrides are ionic solids with high melting points.**
- Alkali metal hydrides are indeed ionic compounds formed by the transfer of electrons from the metal to hydrogen. The strong ionic bonds result in high melting points due to the high lattice energy associated with these compounds.
- **Conclusion:** This statement is **correct**.

4. **Statement 4: Concentrated solution of alkali metals in liquid ammonia is paramagnetic in nature.**
- In concentrated solutions of alkali metals in liquid ammonia, the unpaired electrons present tend to pair up, resulting in a diamagnetic nature rather than paramagnetic. Therefore, this statement is incorrect.
- **Conclusion:** This statement is **incorrect**.

### Final Answer:
The incorrect statement is **Statement 4**: "Concentrated solution of alkali metals in liquid ammonia is paramagnetic in nature."

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