What is the correct order of `2^(nd)` ionisation energy ?

Options

A. `F lt N lt C lt O`
B. `N lt C lt F lt O`
C. `C lt N lt F lt O`
D. `O lt C lt F lt N`

Explanation

To determine the correct order of second ionization energy for the elements carbon (C), nitrogen (N), oxygen (O), and fluorine (F), we need to analyze the electronic configurations of their unipositive cations (C⁺, N⁺, O⁺, and F⁺) and understand the stability of these configurations.

### Step-by-Step Solution:

1. **Identify the electronic configurations of the neutral atoms:**
- Carbon (C): 1s² 2s² 2p²
- Nitrogen (N): 1s² 2s² 2p³
- Oxygen (O): 1s² 2s² 2p⁴
- Fluorine (F): 1s² 2s² 2p⁵

2. **Determine the electronic configurations of the unipositive cations:**
- For Carbon (C⁺): Removing one electron from C gives us 1s² 2s² 2p¹.
- For Nitrogen (N⁺): Removing one electron from N gives us 1s² 2s² 2p².
- For Oxygen (O⁺): Removing one electron from O gives us 1s² 2s² 2p³.
- For Fluorine (F⁺): Removing one electron from F gives us 1s² 2s² 2p⁴.

3. **Analyze the stability of the electronic configurations:**
- C⁺ (1s² 2s² 2p¹) has a less stable configuration due to having a single electron in the p-orbital.
- N⁺ (1s² 2s² 2p²) has a more stable configuration than C⁺, as it has paired electrons in the p-orbital.
- O⁺ (1s² 2s² 2p³) has a half-filled p-orbital, which is particularly stable.
- F⁺ (1s² 2s² 2p⁴) has a stable configuration as well, but it is less stable than O⁺ due to the increased electron-electron repulsion in the p-orbitals.

4. **Order the second ionization energies based on stability:**
- The second ionization energy is generally higher for more stable configurations. Thus, we can rank them as follows:
- O⁺ has the highest second ionization energy due to its stable half-filled p-orbital.
- N⁺ follows, as it has a stable configuration with paired electrons.
- F⁺ comes next, as it is stable but less so than O⁺ and N⁺.
- C⁺ has the lowest second ionization energy due to its unstable configuration.

5. **Final order of second ionization energy:**
- The correct order of second ionization energy is:
**O⁺ > N⁺ > F⁺ > C⁺**