Which of the following represents the correct order of increasing electron gain enthalpy with negative sign for the elements O, S, F and Cl?

Options

A. `Cl lt F lt O lt S `
B. `O lt S lt F lt Cl`
C. ` F lt S lt O lt Cl`
D. ` S lt O lt Cl lt F `

Answer

To determine the correct order of increasing electron gain enthalpy (with negative sign) for the elements O (Oxygen), S (Sulfur), F (Fluorine), and Cl (Chlorine), we need to consider the trends in electron gain enthalpy across the periodic table.

### 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. A more negative value indicates a greater tendency to gain an electron.

2. **Periodic Trends**:
- As we move from left to right across a period, the electron gain enthalpy generally becomes more negative (i.e., increases).
- As we move down a group, the electron gain enthalpy generally becomes less negative (i.e., decreases).

3. **Position of Elements**:
- Oxygen (O) and Sulfur (S) are in Group 16, with Oxygen being above Sulfur.
- Fluorine (F) and Chlorine (Cl) are in Group 17, with Fluorine being above Chlorine.

4. **Comparing Electron Gain Enthalpy**:
- For Fluorine and Chlorine: Fluorine has a smaller atomic radius and higher electronegativity compared to Chlorine, which would suggest that Fluorine should have a more negative electron gain enthalpy. However, due to the high electron-electron repulsion in the small size of Fluorine, its electron gain enthalpy is actually less negative than that of Chlorine.
- For Oxygen and Sulfur: Similarly, Oxygen has a smaller atomic radius than Sulfur, but due to the same electron-electron repulsion, Sulfur has a more negative electron gain enthalpy than Oxygen.

5. **Final Order**:
- Based on the trends and comparisons:
- Chlorine (Cl) > Sulfur (S) > Oxygen (O) > Fluorine (F)
- Therefore, the order of increasing electron gain enthalpy (with negative sign) is:
- Cl > S > O > F

### Conclusion:
The correct order of increasing electron gain enthalpy (with negative sign) for the elements O, S, F, and Cl is:
**Cl > S > O > F** (Option B).