In which of the following electron distribution in ground state, only the Hund's rule is violated?

Options

A.
B.
C.
D.

Explanation

To determine which electron distribution violates only Hund's rule, we first need to understand what Hund's rule states. Hund's rule indicates that electrons will fill degenerate orbitals (orbitals of the same energy) singly before pairing up. This means that if we have multiple orbitals available (like p, d, or f orbitals), we should fill each orbital with one electron first before we start pairing them.

### Step-by-Step Solution:

1. **Understand Hund's Rule**:
- According to Hund's rule, when electrons occupy orbitals of the same energy (like the three p orbitals), they will first fill each orbital singly before any pairing occurs.

2. **Review the Options**:
- We need to analyze the given options to see which one violates only Hund's rule.

3. **Analyze Each Option**:
- **Option A**: If the electron configuration shows paired electrons in the p orbitals before all orbitals have one electron, then Hund's rule is violated.
- **Option B**: If all electrons are singly occupied in the p orbitals, then Hund's rule is followed.
- **Option C**: If there are paired electrons in the same orbital without filling the other orbitals first, then Hund's rule is violated.
- **Option D**: If all electrons are filled according to both Hund's rule and Pauli's exclusion principle, then neither rule is violated.

4. **Identify the Correct Option**:
- After analyzing the options, we find that **Option A** violates Hund's rule because it shows paired electrons in the p orbitals before all orbitals have been singly occupied.

5. **Conclusion**:
- The correct answer is **Option A**, where only Hund's rule is violated.