In each of the following questions a Statement of Assertion (A ) is given followed by a corresponding statement of Reason (R ) Just below it . Of the statement mark the correct answer as
Assertion . Noble gases have positive electron gain enthalpy.
Reason. Noble gases have stable closed shell electronic configuration .

Explanation

To solve the question, we need to analyze both the Assertion (A) and the Reason (R) statements provided.

**Step 1: Analyze the Assertion (A)**
- The assertion states: "Noble gases have positive electron gain enthalpy."
- Noble gases are known for their stable electronic configuration, which is a full outer shell of electrons. This stability means that noble gases do not tend to gain additional electrons easily. In fact, when an electron is added to a noble gas atom, it requires energy rather than releasing energy. Therefore, the electron gain enthalpy for noble gases is positive.

**Step 2: Analyze the Reason (R)**
- The reason states: "Noble gases have stable closed shell electronic configuration."
- This statement is true. Noble gases possess a complete outer shell of electrons (usually 8 electrons, except for Helium, which has 2), making them very stable and unreactive. This stability is the reason why they have a positive electron gain enthalpy, as they do not favor gaining electrons.

**Step 3: Determine the relationship between A and R**
- The assertion is incorrect because noble gases do not have a positive electron gain enthalpy; rather, they have a negative or zero value. However, the reason is correct as it explains the stability of noble gases due to their closed shell configuration.
- Since the assertion is false and the reason is true, the correct answer is that the assertion is not supported by the reason.

**Final Answer:**
- Assertion (A) is false, and Reason (R) is true.

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