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 periods and down groups in the periodic table.

### Step-by-step Solution:

1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy refers to the energy change 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.

2. **Periodic Trends**:
- **Across a Period**: Electron gain enthalpy generally becomes more negative (increases) as you move from left to right across a period due to increasing nuclear charge.
- **Down a Group**: Electron gain enthalpy generally becomes less negative (decreases) as you move down a group due to increased atomic size and shielding effect.

3. **Comparing the Elements**:
- **Fluorine (F)**: Being in the second period, it has a high electron gain enthalpy, but due to its small size, it experiences significant electron-electron repulsion when gaining an electron.
- **Chlorine (Cl)**: Although it is larger than fluorine, it has a higher electron gain enthalpy than fluorine because it is more stable when gaining an electron.
- **Oxygen (O)**: Has a relatively high electron gain enthalpy, but it is less than that of chlorine.
- **Sulfur (S)**: Being in the third period, it has a lower electron gain enthalpy compared to oxygen.

4. **Order of Electron Gain Enthalpy**:
- Based on the above analysis, we can summarize the electron gain enthalpy values as follows:
- S < O < Cl < F
- However, since we are looking for the order of increasing electron gain enthalpy with negative sign, we will express this as:
- S > O > Cl > F

### Final Answer:
The correct order of increasing electron gain enthalpy (with negative sign) is:
**S < O < Cl < F**