Which of the following configurations does not follow Hund's rule of maximum multiplicity?

Options

A. `1s^(2)2s^(2)2p^(6)3s^(2)3p^(2)`
B. `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^(6)`
C. `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(1)3d^(5)`
D. `1s^(2)2s^(2)2p^(6)3s^(2)3p^(4)4s^(2)`

Explanation

To determine which electron configuration does not follow Hund's Rule of Maximum Multiplicity, we first need to understand what Hund's Rule states. Hund's Rule states that for orbitals of the same energy (degenerate orbitals), electrons will fill each orbital singly before pairing up. This maximizes the total spin and, therefore, the multiplicity of the configuration.

Let's analyze the given options step by step:

### Step 1: Understand the configurations
We have four configurations to analyze:
1. **Option 1:** 1s² 2s² 2p⁶ 3s² 3p⁶
2. **Option 2:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶
3. **Option 3:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵
4. **Option 4:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p²

### Step 2: Analyze each option
1. **Option 1:** This configuration is completely filled up to 3p, which is correct according to the Aufbau principle and Hund's Rule.

2. **Option 2:** This configuration fills the 4s orbital before the 3d orbital, which is also correct. The 3d orbital can hold a maximum of 10 electrons, and filling follows Hund's Rule.

3. **Option 3:** Here, we have 4s¹ and 3d⁵. The 3d orbital is half-filled, which is favorable according to Hund's Rule. This configuration is acceptable as it maximizes the multiplicity.

4. **Option 4:** This configuration has 4s² and 4p². The 4p orbitals should be filled singly first before any pairing occurs. Since 4p can hold a maximum of 6 electrons, this configuration does not follow Hund's Rule as it suggests pairing before all orbitals are singly occupied.

### Conclusion
The configuration that does not follow Hund's Rule of Maximum Multiplicity is **Option 4: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p²**.

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