Which of the following element has the highest ionisation enregy ?

Options

A. Carbon
B. Boron
C. Oxygen
D. Nitrogen

Explanation

To determine which element has the highest ionization energy among the given options (Carbon, Boron, Oxygen, and Nitrogen), we need to analyze the electronic configurations of each element and understand the concept of ionization energy.

### Step-by-Step Solution:

1. **Understand Ionization Energy**:
- Ionization energy is the energy required to remove an electron from an atom in the gas phase. Generally, elements with a stable electronic configuration have higher ionization energies.

2. **List the Elements and Their Electronic Configurations**:
- **Carbon (C)**: 1s² 2s² 2p²
- **Boron (B)**: 1s² 2s² 2p¹
- **Oxygen (O)**: 1s² 2s² 2p⁴
- **Nitrogen (N)**: 1s² 2s² 2p³

3. **Analyze Stability of Electronic Configurations**:
- A stable electronic configuration often corresponds to fully filled or half-filled subshells.
- Nitrogen (N) has the configuration 1s² 2s² 2p³, which is half-filled in the 2p subshell. Half-filled subshells are particularly stable.

4. **Compare Ionization Energies**:
- Generally, as we move from left to right across a period in the periodic table, ionization energy increases due to increasing nuclear charge and decreasing atomic radius.
- Among the given elements, Nitrogen has a half-filled p subshell, which contributes to its stability and higher ionization energy compared to the others.

5. **Conclusion**:
- Based on the analysis, Nitrogen (N) has the highest ionization energy among the listed elements.

### Final Answer:
The element with the highest ionization energy is **Nitrogen (N)**.

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