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

Options

A. `F gt Cl gt Br gt I`
B. `F lt Cl lt Br lt I `
C. `F lt Cl gt Br gt I`
D. `F lt Cl lt Br lt I`

Explanation

To determine the correct order of energy released in electron gain enthalpy among halogens, we need to analyze the trends in electron gain enthalpy for the halogen group (Group 17) elements: fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

### Step-by-Step Solution:

1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy is defined as the amount of energy released when an atom gains an electron. A more negative value indicates a greater tendency to gain an electron.

2. **Analyzing the Halogens**:
- The halogens include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). As we move down the group from fluorine to iodine, the atomic size increases.

3. **Effect of Atomic Size**:
- As the atomic size increases, the effective nuclear charge experienced by the incoming electron decreases. This is because the outermost electrons are further away from the nucleus, leading to a weaker attraction for the incoming electron.

4. **Comparing Fluorine and Chlorine**:
- Although fluorine is more electronegative than chlorine, it has a smaller atomic size. The incoming electron in fluorine experiences significant electron-electron repulsion in the 2p subshell, which makes it less favorable for the atom to gain an additional electron compared to chlorine, where the incoming electron does not face as much repulsion in the larger 3p subshell.

5. **Order of Electron Gain Enthalpy**:
- Based on the above analysis:
- Chlorine (Cl) has the most negative electron gain enthalpy (highest tendency to gain an electron).
- Fluorine (F) follows, but with a less negative value due to repulsion.
- Bromine (Br) is next, with less tendency than fluorine and chlorine.
- Iodine (I) has the least negative electron gain enthalpy due to its larger size and lower effective nuclear charge.

6. **Final Order**:
- The correct order of electron gain enthalpy among halogens is:
- Cl > F > Br > I

### Answer:
The correct order of amount of energy released in electron gain (electron gain enthalpy) among halogens is:
**Cl > F > Br > I**