Assertion: In some cases oxygen shows positive oxidation number though it is an electronegative element.
Reason: Fluorine is more electronegative than oxygen.

Options

A. If both A and R are true and R is the correct explanation of A.
B. If both A and R are true but R is not the correct explanation of A.
C. If A is true but R is false
D. If A is false but R is true.

Explanation

To solve the question, we need to analyze the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that "In some cases, oxygen shows a positive oxidation number though it is an electronegative element."

- **Analysis**: Oxygen is indeed an electronegative element, typically having a negative oxidation state in most of its compounds. However, there are exceptions where oxygen can exhibit a positive oxidation state, particularly when bonded to more electronegative elements like fluorine.

### Step 2: Understand the Reason
The reason states that "Fluorine is more electronegative than oxygen."

- **Analysis**: This statement is true. Fluorine is the most electronegative element in the periodic table, and oxygen is the second most electronegative element. This difference in electronegativity is crucial in determining the oxidation states of elements in compounds.

### Step 3: Provide an Example
To illustrate the assertion, we can consider the compound oxygen difluoride (OF₂).

- **Calculation of Oxidation State**:
- Let the oxidation state of oxygen be \( X \).
- The oxidation state of each fluorine atom is \(-1\).
- The overall charge of the compound is neutral (0).

Therefore, we can set up the equation:
\[ X + 2(-1) = 0 \]
Simplifying this gives:
\[ X - 2 = 0 \implies X = +2 \]
Thus, in OF₂, oxygen has a positive oxidation state of +2.

### Step 4: Conclusion
Since the assertion is true (oxygen can show a positive oxidation state in certain compounds) and the reason is also true (fluorine is more electronegative than oxygen), and the reason correctly explains the assertion, we conclude that:

**Both assertion and reason are true, and the reason is the correct explanation of the assertion.**

### Final Answer
The correct option is: **Both assertion and reason are true, and reason is the correct explanation of assertion.**

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