Assertion : For noble gases, valency is zero. Reason : Noble gases have 8 valence electrons.

Options

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

Explanation

To analyze the assertion and reason provided in the question, we can break it down into a step-by-step solution:

### Step 1: Understand the Assertion
The assertion states that "For noble gases, valency is zero."
- Valency refers to the combining capacity of an element, which is determined by the number of electrons an atom can gain, lose, or share during a chemical reaction.

### Step 2: Understand the Reason
The reason states that "Noble gases have 8 valence electrons."
- Noble gases, which include helium, neon, argon, krypton, xenon, and radon, have a complete outer shell of electrons. For most noble gases (except helium, which has 2), this means they have 8 valence electrons.

### Step 3: Connect the Assertion and Reason
- Since noble gases have a complete outer shell with 8 valence electrons, they do not need to gain, lose, or share electrons to achieve stability. Therefore, they do not readily react with other elements. This lack of reactivity is why their valency is considered to be zero.

### Step 4: Conclusion
- Both the assertion and the reason are true. The assertion is correct because noble gases do have a valency of zero, and the reason is also correct because noble gases indeed have 8 valence electrons.

### Final Answer
- The assertion is true, and the reason is true, and the reason correctly explains the assertion.

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