Assertion : Noble gases are diamagnetic atoms
Reason :The atomic numbers of noble gases are even and all the orbitals are doubly occupied by the electrons

Options

A. If both (A) and (R ) are correct and (R ) is the correct explanation of (A)
B. If both (A) and (R ) are correct,but (R ) is the correct explanation of (A)
C. If (A) is correct but (R ) is incorrect
D. If (A) is incorrect but (R ) is correct

Answer

To solve the question regarding the assertion and reason about noble gases, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that noble gases are diamagnetic atoms.
- **Definition of Diamagnetic**: An atom is considered diamagnetic if it has no unpaired electrons. This means all its electrons are paired.

2. **Identifying Noble Gases**: Noble gases are elements found in Group 18 of the periodic table. The noble gases include:
- Helium (He)
- Neon (Ne)
- Argon (Ar)
- Krypton (Kr)
- Xenon (Xe)
- Radon (Rn)

3. **Checking the Electronic Configuration**:
- The electronic configurations of noble gases are as follows:
- Helium (He): 1s²
- Neon (Ne): 1s² 2s² 2p⁶
- Argon (Ar): 1s² 2s² 2p⁶ 3s² 3p⁶
- Krypton (Kr): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p⁶
- Xenon (Xe): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p⁶ 5s² 5p⁶
- Radon (Rn): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p⁶ 5s² 5p⁶ 6s² 6p⁶

4. **Analyzing Electron Pairing**:
- In all the noble gases, the electronic configurations show that all orbitals are fully filled, meaning every electron is paired. This confirms that noble gases are indeed diamagnetic.

5. **Understanding the Reason**: The reason states that the atomic numbers of noble gases are even and all the orbitals are doubly occupied by the electrons.
- **Atomic Numbers**: The atomic numbers of noble gases are indeed even (He: 2, Ne: 10, Ar: 18, Kr: 36, Xe: 54, Rn: 86).
- **Doubly Occupied Orbitals**: The statement that all orbitals are doubly occupied is also correct, as each orbital in the noble gases has paired electrons.

6. **Conclusion**:
- Since both the assertion and reason are true, and the reason correctly explains the assertion, we conclude that the correct option is that both the assertion and reason are correct, and the reason is the correct explanation of the assertion.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion.