Which one of the following outer electron configurations is not correct ?

Options

A. `N:2s^2 2p^3`
B. `O:2s^2 2p^4`
C. `Al:3s^2 3p^3`
D. `B:2s^2 2p^1`

Answer

To determine which outer electron configuration is not correct among the given options for Nitrogen, Oxygen, Aluminium, and Boron, we will analyze the outer electron configurations based on their atomic numbers.

### Step-by-Step Solution:

1. **Identify Atomic Numbers**:
- Nitrogen (N) has an atomic number of 7.
- Oxygen (O) has an atomic number of 8.
- Aluminium (Al) has an atomic number of 13.
- Boron (B) has an atomic number of 5.

2. **Determine Electron Configurations**:
- For Nitrogen (N):
- The electron configuration is 1s² 2s² 2p³.
- The outer electron configuration is 2s² 2p³.
- For Oxygen (O):
- The electron configuration is 1s² 2s² 2p⁴.
- The outer electron configuration is 2s² 2p⁴.
- For Aluminium (Al):
- The electron configuration is 1s² 2s² 2p⁶ 3s² 3p¹.
- The outer electron configuration is 3s² 3p¹.
- For Boron (B):
- The electron configuration is 1s² 2s² 2p¹.
- The outer electron configuration is 2s² 2p¹.

3. **Compare Given Configurations**:
- Check the provided outer electron configurations:
- Nitrogen: 2s² 2p³ (Correct)
- Oxygen: 2s² 2p⁴ (Correct)
- Aluminium: 3s² 3p³ (Incorrect, should be 3s² 3p¹)
- Boron: 2s² 2p¹ (Correct)

4. **Conclusion**:
- The outer electron configuration for Aluminium (3s² 3p³) is not correct. The correct configuration should be 3s² 3p¹.

### Final Answer:
The outer electron configuration that is not correct is for Aluminium: **3s² 3p³**.