Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is:

Options

A. `F gt CI gt Br gt I`
B. `F lt CI lt Bt lt I`
C. `F lt CI gt Br gt I`
D. `CI gt Br gt F gt I`

Answer

To determine the correct order of electron gain enthalpy among halogens, we will analyze the trends in the halogen group (Group 17) of the periodic table.

### Step-by-Step Solution:

1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy is defined as the amount of energy released when an electron is added to a neutral atom in the gaseous state. A more negative value indicates that more energy is released, which means a greater tendency to gain an electron.

2. **Trends in the Halogen Group**:
- As we move down the group from fluorine (F) to iodine (I), the atomic size increases. This increase in size affects the electron gain enthalpy.

3. **Analyzing Fluorine**:
- Fluorine has a very small atomic radius, which means that the incoming electron experiences significant electron-electron repulsion due to the already existing electrons in the valence shell. This leads to a less negative (or less exothermic) electron gain enthalpy compared to what we might expect.

4. **Analyzing Chlorine and Bromine**:
- Chlorine (Cl) is larger than fluorine, and the electron gain enthalpy becomes more negative as we move from fluorine to chlorine. Chlorine can accommodate an additional electron more easily than fluorine due to reduced repulsion.

5. **Analyzing Iodine**:
- Iodine (I) is even larger than chlorine, and thus, the electron gain enthalpy becomes less negative again. The larger atomic size means that the added electron is further from the nucleus, which reduces the effective nuclear attraction.

6. **Conclusion**:
- The correct order of electron gain enthalpy for halogens from most negative to least negative is:
- **Cl > F > Br > I**
- This means that chlorine has the highest electron gain enthalpy, followed by fluorine, bromine, and iodine.

### Final Answer:
The correct order of electron gain enthalpy among halogens is: **Cl > F > Br > I**.