Which of the following is correct for electron gain enthalpy (with -ve sign) of halogens?

Options

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

Answer

To solve the question regarding the electron gain enthalpy of halogens, we need to understand the trend of electron gain enthalpy in the halogen group (Group 17) of the periodic table. The halogens include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

### Step-by-Step Solution:

1. **Understanding Electron Gain Enthalpy**:
Electron gain enthalpy is the energy change when an electron is added to a neutral atom in the gas phase. It is typically expressed with a negative sign, indicating that energy is released when an electron is added.

2. **Trends in Electron Gain Enthalpy**:
- As we move down the group from fluorine to iodine, the size of the atoms increases.
- Larger atomic size means that the added electron is further from the nucleus and experiences less electrostatic attraction.
- Therefore, the electron gain enthalpy becomes less negative (or less exothermic) as we move down the group.

3. **Order of Electron Gain Enthalpy**:
- Fluorine has the most negative electron gain enthalpy, meaning it releases the most energy when gaining an electron.
- Chlorine follows, then bromine, and finally iodine has the least negative electron gain enthalpy.
- The correct order from most negative to least negative is:
- Fluorine (F) > Chlorine (Cl) > Bromine (Br) > Iodine (I)

4. **Analyzing the Options**:
- We need to identify the correct statement regarding the electron gain enthalpy of halogens based on the trend we established.
- The correct statement would reflect that fluorine has the most negative electron gain enthalpy, followed by chlorine, bromine, and iodine having the least negative.

5. **Conclusion**:
- Based on the analysis, the correct option is the one that states that fluorine has the most negative electron gain enthalpy and iodine has the least negative.

### Final Answer:
The correct option is **Option 3**: Fluorine has the most negative electron gain enthalpy, and iodine has the least negative.