In the following questions, a statement of assertion (A) is followed by a statement of reason (R )
A : `PCl_(5)` exist but `NCl_(5)` does not
R : Nitrogen is highly inert.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements , then mark (4).

Answer

To solve the question regarding the assertion (A) and reason (R) about the existence of \( PCl_5 \) and the non-existence of \( NCl_5 \), we will analyze both statements step by step.

### Step 1: Analyze the Assertion (A)
**Assertion (A)**: \( PCl_5 \) exists but \( NCl_5 \) does not.

- **Explanation**:
- \( PCl_5 \) (phosphorus pentachloride) exists because phosphorus (P) has the ability to expand its octet due to the presence of d-orbitals. Phosphorus can accommodate more than eight electrons in its valence shell, allowing it to form five bonds with chlorine atoms.
- On the other hand, nitrogen (N) does not have d-orbitals available for bonding. Its electronic configuration is \( 1s^2 2s^2 2p^3 \), meaning it can only form a maximum of four bonds (as in \( NCl_3 \)). Therefore, \( NCl_5 \) cannot exist because nitrogen cannot accommodate five bonding pairs of electrons.

### Step 2: Analyze the Reason (R)
**Reason (R)**: Nitrogen is highly inert.

- **Explanation**:
- While it is true that nitrogen (in its diatomic form \( N_2 \)) is quite inert due to the strong triple bond between the nitrogen atoms, this does not directly explain why \( NCl_5 \) does not exist. The inertness of nitrogen is related to its stability in the molecular form \( N_2 \), but it does not address the electronic structure and bonding capabilities of nitrogen in the context of forming \( NCl_5 \).

### Step 3: Conclusion
- **Assertion is True**: \( PCl_5 \) exists, but \( NCl_5 \) does not due to the absence of d-orbitals in nitrogen.
- **Reason is True**: Nitrogen is highly inert, but this does not explain the assertion regarding the existence of \( PCl_5 \) and the non-existence of \( NCl_5 \).

### Final Answer
Both the assertion and reason are true, but the reason does not correctly explain the assertion. Therefore, the correct option is:
**Option 2**: Both assertion and reason are true, but reason is not the correct explanation of assertion.

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