The element with half-filled outermost electronic configuration

Options

A. aluminium
B. magnesium
C. boron
D. nitrogen

Explanation

To find the element with a half-filled outermost electronic configuration from the given options (Aluminum, Magnesium, Boron, or Nitrogen), we need to analyze the electronic configurations of each element step by step.

### Step-by-Step Solution:

1. **Identify the Electronic Configurations**:
- **Aluminum (Al)**: The atomic number is 13. Its electronic configuration is:
\[ \text{Al: } 1s^2 2s^2 2p^6 3s^2 3p^1 \quad \text{(or in shorthand: [Ne] 3s}^2 3p^1\text{)} \]
- **Magnesium (Mg)**: The atomic number is 12. Its electronic configuration is:
\[ \text{Mg: } 1s^2 2s^2 2p^6 3s^2 \quad \text{(or in shorthand: [Ne] 3s}^2\text{)} \]
- **Boron (B)**: The atomic number is 5. Its electronic configuration is:
\[ \text{B: } 1s^2 2s^2 2p^1 \quad \text{(or in shorthand: [He] 2s}^2 2p^1\text{)} \]
- **Nitrogen (N)**: The atomic number is 7. Its electronic configuration is:
\[ \text{N: } 1s^2 2s^2 2p^3 \quad \text{(or in shorthand: [He] 2s}^2 2p^3\text{)} \]

2. **Determine the Half-Filled Configuration**:
- A half-filled subshell occurs when the number of electrons in a subshell is equal to half the maximum capacity of that subshell.
- For the **p subshell**, which can hold a maximum of 6 electrons, half-filled means having 3 electrons.

3. **Analyze Each Element**:
- **Aluminum**: The outermost configuration is \(3s^2 3p^1\). The p subshell is not half-filled (only 1 electron).
- **Magnesium**: The outermost configuration is \(3s^2\). There are no p electrons, so it cannot be half-filled.
- **Boron**: The outermost configuration is \(2s^2 2p^1\). The p subshell has only 1 electron, which is not half-filled.
- **Nitrogen**: The outermost configuration is \(2s^2 2p^3\). The p subshell has 3 electrons, which is exactly half-filled.

4. **Conclusion**:
- The element with a half-filled outermost electronic configuration is **Nitrogen**.

### Final Answer:
The element with half-filled outermost electronic configuration is **Nitrogen**.