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`

Answer

To determine the correct order of ionization energies for the given elements (F, Cl, F⁻, Cl⁻), we need to analyze the trends in ionization energy based on atomic structure and periodic trends.

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
- Ionization energy is the energy required to remove an electron from an atom in its gaseous state. The higher the ionization energy, the more difficult it is to remove an electron.

2. **Comparing Neutral Atoms**:
- **Fluorine (F)** and **Chlorine (Cl)** are both halogens.
- Fluorine is smaller in size compared to chlorine because it has fewer electron shells.
- Since ionization energy increases with decreasing atomic size (as the outermost electrons are held more tightly by the nucleus), **F** will have a higher ionization energy than **Cl**.

3. **Considering Anions**:
- **F⁻** and **Cl⁻** are anions, meaning they have gained an extra electron.
- The addition of an electron increases the size of the atom (anion) because of increased electron-electron repulsion.
- Consequently, the effective nuclear charge experienced by the outermost electrons decreases, making it easier to remove an electron from these anions compared to their neutral counterparts.

4. **Comparing Ionization Energies of Anions**:
- For **F⁻**, the outermost electron is held more tightly due to the higher electronegativity of fluorine compared to chlorine. Thus, it will have a higher ionization energy than **Cl⁻**.
- Therefore, the order of ionization energy from highest to lowest will be:
- F > Cl > F⁻ > Cl⁻

5. **Final Order**:
- The correct order of ionization energies is:
- **F > Cl > F⁻ > Cl⁻**

### Conclusion:
The correct order of ionization energies is F > Cl > F⁻ > Cl⁻.