(A): All noble gases are monoatomic
(R): Noble gas atom is stable and does not dimerise or polymerise

Options

A. Both A & R are true, R is the correct explanation of A
B. Both A & R are true, R is not correct explanation of A
C. A is true, R is false
D. A is false, R is true

Answer

To solve the assertion-reason question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step 1: Understand the Assertion
**Assertion (A):** All noble gases are monoatomic.

- Noble gases are found in Group 18 of the periodic table, which includes helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).
- These gases exist as single atoms rather than molecules. This means they are monoatomic.

**Conclusion for Step 1:** The assertion is true.

### Step 2: Understand the Reason
**Reason (R):** Noble gas atom is stable and does not dimerize or polymerize.

- Noble gases have a complete outer shell of electrons, which is known as the octet rule (except for helium, which has a complete shell with 2 electrons).
- This complete electron configuration makes noble gases very stable, and they do not need to bond with other atoms to achieve stability.
- Dimerization and polymerization are processes where atoms bond together to achieve a more stable electron configuration. Since noble gases already have a stable configuration, they do not engage in these processes.

**Conclusion for Step 2:** The reason is also true.

### Step 3: Determine the Relationship Between A and R
- The reason (R) explains why the assertion (A) is true. The stability of noble gases due to their complete octet is the reason they are monoatomic and do not form diatomic or polyatomic structures.

### Final Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is that both A and R are true, and R is the correct explanation of A.

### Summary of the Solution
- **Assertion (A):** True
- **Reason (R):** True
- **Conclusion:** Both A and R are true, and R is the correct explanation of A.

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