Assertion: Nitrogen is unreactive at room temperature but becomes reactive at elevated temperature (on heating or in the presence of catalysts).
Reason: In nitrogen molecule, there is extensive delocalisation of electrons.

Options

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

Answer

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

### Step 1: Analyze the Assertion
The assertion states that nitrogen is unreactive at room temperature but becomes reactive at elevated temperatures (on heating or in the presence of catalysts).

- **Explanation**: Nitrogen (N₂) is a diatomic molecule with a triple bond between the two nitrogen atoms, which makes it very stable and unreactive under normal conditions. However, when the temperature increases or when a catalyst is present, the energy provided can overcome the bond strength of the triple bond, allowing nitrogen to react with other substances.

### Step 2: Analyze the Reason
The reason given is that in the nitrogen molecule, there is extensive delocalization of electrons.

- **Explanation**: This statement is incorrect. In the nitrogen molecule (N₂), the electrons are localized in the triple bond between the two nitrogen atoms. There is no extensive delocalization of electrons as seen in resonance structures of some other molecules. The stability of the N₂ molecule is primarily due to the strong triple bond, not due to electron delocalization.

### Step 3: Conclusion
Based on the analysis:
- The assertion is **true**: Nitrogen is indeed unreactive at room temperature and becomes reactive at higher temperatures or in the presence of catalysts.
- The reason is **false**: There is no extensive delocalization of electrons in the nitrogen molecule; the electrons are localized in the triple bond.

Thus, the correct answer is that the assertion is true, and the reason is false.

### Final Answer
Assertion: True
Reason: False

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