Assertion (A): Sodium reacts with oxygen to form `Na_(2)O_(2)` whereas potassium reacts with oxygen to form `KO_(2)`.
Reason (R ): Potassium is more reactive than sodium.

Options

A. If both (A) and (R ) are correct and (R ) is the correct explanation of (A).
B. If both (A) and (R ) are correct, but (R ) is not the correct explanation of (A).
C. If (A) is correct, but (R ) is incorrect.
D. If (A) is incorrect, but (R ) is correct.

Explanation

To solve the assertion and reason question, let's break it down step by step:

### Step 1: Analyze the Assertion
The assertion states that sodium reacts with oxygen to form sodium peroxide (`Na2O2`), while potassium reacts with oxygen to form potassium superoxide (`KO2`).

- **Sodium and Oxygen Reaction**: Sodium can react with oxygen to form sodium peroxide due to its ability to stabilize the peroxide ion (`O2^2-`).
- **Potassium and Oxygen Reaction**: Potassium, being larger in size, can stabilize the superoxide ion (`O2^-`) and thus forms potassium superoxide.

### Step 2: Analyze the Reason
The reason given is that potassium is more reactive than sodium.

- **Reactivity of Alkali Metals**: It is true that potassium is more reactive than sodium. This is due to its lower ionization enthalpy, which makes it easier for potassium to lose its outer electron compared to sodium.

### Step 3: Evaluate the Relationship Between Assertion and Reason
Now, we need to determine if the reason correctly explains the assertion.

- **Correctness of Assertion**: The assertion is correct; sodium forms peroxide while potassium forms superoxide.
- **Correctness of Reason**: While the reason that potassium is more reactive than sodium is correct, it does not explain why sodium forms peroxide and potassium forms superoxide. The actual reason lies in the size and charge density of the ions, not just their reactivity.

### Conclusion
- **Assertion (A)**: True
- **Reason (R)**: True, but it does not explain the assertion correctly.

### Final Answer
Both statements are correct, but the reason does not adequately explain the assertion. Therefore, the answer is **B**.

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