Which is the correct order of ionization energies?

Options

A. `F^(-) gt F gt Cl^(-) gt Cl`
B. `F gt Cl gt Cl^(-) gt F^(-)`
C. `F^(-) gt Cl^(-) gt Cl gt F`
D. `F^(-) gt Cl^(-) gt F gt Cl`

Explanation

To determine the correct order of ionization energies among the given species (F⁻, Cl⁻, F, and Cl), we need to analyze the factors affecting ionization energy and the characteristics of each species.

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
Ionization energy (IE) is the energy required to remove an electron from an isolated gaseous atom or ion. Generally, the more tightly an electron is held, the higher the ionization energy.

2. **Analyzing the Species**:
- **F (Fluorine)**: Has 9 protons and 9 electrons. It has a high ionization energy due to its small atomic size and high effective nuclear charge.
- **F⁻ (Fluoride ion)**: Has 9 protons and 10 electrons. The extra electron leads to increased electron-electron repulsion, making it easier to remove an electron compared to neutral fluorine.
- **Cl (Chlorine)**: Has 17 protons and 17 electrons. It has a larger atomic size than fluorine, resulting in lower ionization energy than fluorine.
- **Cl⁻ (Chloride ion)**: Has 17 protons and 18 electrons. Similar to F⁻, the additional electron increases electron-electron repulsion, making it easier to remove an electron compared to neutral chlorine.

3. **Comparing Ionization Energies**:
- **F vs. F⁻**: F has a higher ionization energy than F⁻ because F⁻ has an additional electron that experiences repulsion.
- **Cl vs. Cl⁻**: Cl has a higher ionization energy than Cl⁻ for the same reason as above.
- **F vs. Cl**: F has a higher ionization energy than Cl due to its smaller size and higher effective nuclear charge.
- **F⁻ vs. Cl⁻**: Cl⁻ has a lower ionization energy than F⁻ because Cl⁻ is larger and has more electron-electron repulsion.

4. **Establishing the Order**:
Based on the analysis:
- F > Cl > F⁻ > Cl⁻
This indicates that the order of increasing ionization energy is Cl⁻ < F⁻ < Cl < F.

### Final Answer:
The correct order of ionization energies is: **Cl⁻ < F⁻ < Cl < F**.