Correct order of electron gain enthalpy (Kj/mole) of F, Cl, Br, I

Options

A. `-296,-325,-333,-349`
B. `-333,-349,-325,-296`
C. `-349,-333,-325,-296`
D. `-325,-333,-349,-296`

Answer

To determine the correct order of electron gain enthalpy (in kJ/mole) for the halogens: Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I), we can follow these steps:

### Step 1: Understand 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 a greater tendency to gain an electron.

### Step 2: Analyze the Halogens
The halogens in question are:
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)

### Step 3: Consider Atomic Size and Electron Repulsion
- **Fluorine** is the smallest atom among these halogens, which leads to significant electron-electron repulsion when an additional electron is added. This repulsion results in a less negative (or lower) electron gain enthalpy.
- **Chlorine**, being larger than fluorine, has less electron-electron repulsion when gaining an electron, resulting in a more negative electron gain enthalpy compared to fluorine.
- **Bromine** and **Iodine** are larger still, and therefore, they will have even less electron-electron repulsion when gaining an electron. Thus, their electron gain enthalpy will be less negative compared to chlorine and fluorine.

### Step 4: Order the Electron Gain Enthalpy
Based on the above reasoning, we can arrange the halogens in order of their electron gain enthalpy from most negative to least negative:
1. Chlorine (Cl) - most negative
2. Fluorine (F)
3. Bromine (Br)
4. Iodine (I) - least negative

### Step 5: Write the Final Order
The correct order of electron gain enthalpy for the halogens is:
**Cl > F > Br > I**

### Step 6: Verify with Values
The approximate values of electron gain enthalpy for these elements are:
- Cl: -349 kJ/mole
- F: -333 kJ/mole
- Br: -325 kJ/mole
- I: -296 kJ/mole

This confirms our order:
1. Cl: -349 kJ/mole
2. F: -333 kJ/mole
3. Br: -325 kJ/mole
4. I: -296 kJ/mole

### Conclusion
Thus, the final order of electron gain enthalpy is:
**Cl > F > Br > I**