Assertion :- `XeF_4` exists while `XeH_4` does not exist.
Reason :- In `XeH_4` d-orbital contraction is absent.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False.

Answer

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

### Step 1: Analyze the Assertion
The assertion states that `XeF4` exists while `XeH4` does not exist.

- **XeF4 (Xenon Tetrafluoride)** is a well-known compound. Xenon can form stable compounds with highly electronegative elements like fluorine due to its ability to expand its octet and accommodate more than eight electrons.
- **XeH4 (Xenon Tetrahydride)**, on the other hand, is not a stable compound. This is primarily because hydrogen is not electronegative enough to stabilize the bond with xenon.

### Step 2: Analyze the Reason
The reason states that in `XeH4`, d-orbital contraction is absent.

- The term "d-orbital contraction" refers to the ability of d-orbitals to participate in bonding. In the case of xenon, it has d-orbitals available for bonding due to its larger atomic size.
- In `XeH4`, the hydrogen atoms do not provide sufficient electronegativity to stabilize the compound, and thus, the absence of effective d-orbital participation leads to instability.

### Step 3: Conclusion
Both the assertion and the reason are true:
- `XeF4` exists due to the high electronegativity of fluorine, which allows xenon to form stable bonds.
- `XeH4` does not exist because hydrogen is not electronegative enough to stabilize the compound, and the absence of effective d-orbital contraction contributes to this instability.

### Final Answer
The correct answer is that both the assertion and reason are true, and the reason is a correct explanation of the assertion.