The correct order of the second ionisation potential of carbon, nitrogen, oxygen and fluorine is

Options

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

Answer

To determine the correct order of the second ionization potential of carbon (C), nitrogen (N), oxygen (O), and fluorine (F), we can follow these steps:

### Step 1: Understand Ionization Potential
Ionization potential (or ionization energy) is the energy required to remove an electron from an atom or ion. The second ionization potential refers to the energy needed to remove a second electron after the first has already been removed.

### Step 2: Write the Electronic Configurations
- **Carbon (C)**: 1s² 2s² 2p²
- **Nitrogen (N)**: 1s² 2s² 2p³
- **Oxygen (O)**: 1s² 2s² 2p⁴
- **Fluorine (F)**: 1s² 2s² 2p⁵

### Step 3: Determine the Configuration After First Ionization
- **C⁺**: 1s² 2s² 2p¹
- **N⁺**: 1s² 2s² 2p²
- **O⁺**: 1s² 2s² 2p³
- **F⁺**: 1s² 2s² 2p⁴

### Step 4: Determine the Configuration After Second Ionization
- **C²⁺**: 1s² 2s²
- **N²⁺**: 1s² 2s² 2p¹
- **O²⁺**: 1s² 2s² 2p²
- **F²⁺**: 1s² 2s² 2p³

### Step 5: Analyze Stability and Nuclear Charge
As we move from carbon to fluorine, the nuclear charge increases, which generally leads to an increase in ionization potential. However, we must also consider the stability of the resulting ions:
- **Oxygen (O²⁺)** has a half-filled stable configuration after the second ionization, which means it requires more energy to remove an electron compared to the others.
- **Fluorine (F²⁺)** has a configuration that is less stable than oxygen but still requires significant energy.
- **Nitrogen (N²⁺)** and **Carbon (C²⁺)** have less stable configurations and will require less energy to ionize.

### Step 6: Establish the Correct Order
Based on the stability and increasing nuclear charge:
1. O (highest second ionization potential due to stability)
2. F
3. N
4. C (lowest second ionization potential)

### Final Answer
The correct order of the second ionization potential of carbon, nitrogen, oxygen, and fluorine is:
**O > F > N > C**