Which one of the following arrangements represents the correct order of electron gain enthalpy of the given atomic species?

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`

Explanation

To determine the correct order of electron gain enthalpy for the given atomic species (Chlorine, Fluorine, Sulfur, and Oxygen), we can follow these steps:

### Step 1: Understand Electron Gain Enthalpy
Electron gain enthalpy is the amount of energy released when an electron is added to a neutral atom in the gaseous state. It is an important property that helps us understand the reactivity of elements.

### Step 2: Identify the Groups of Elements
- Chlorine (Cl) and Fluorine (F) are in Group 17 (halogens).
- Sulfur (S) and Oxygen (O) are in Group 16 (chalcogens).

### Step 3: Analyze Trends in Electron Gain Enthalpy
1. **Across a Period**: Electron gain enthalpy generally increases from left to right across a period due to increasing nuclear charge, which attracts electrons more strongly.
2. **Down a Group**: Electron gain enthalpy generally decreases down a group due to increasing atomic size and electron shielding, which reduces the effective nuclear charge experienced by the added electron.

### Step 4: Compare the Elements
- **Fluorine (F)**: Although it is the most electronegative element, its small size leads to significant electron-electron repulsion when an additional electron is added, resulting in a less negative electron gain enthalpy compared to Chlorine.
- **Chlorine (Cl)**: Larger than Fluorine, it has a more favorable electron gain enthalpy compared to Fluorine.
- **Oxygen (O)**: Smaller than Sulfur but has significant electron-electron repulsion, leading to a less negative electron gain enthalpy than Sulfur.
- **Sulfur (S)**: Larger than Oxygen, and thus has a more favorable electron gain enthalpy compared to Oxygen.

### Step 5: Establish the Order
Based on the above analysis, the order of electron gain enthalpy from most negative (most favorable) to least negative (least favorable) is:
1. Chlorine (Cl)
2. Fluorine (F)
3. Sulfur (S)
4. Oxygen (O)

### Conclusion
The correct order of electron gain enthalpy for the given atomic species is:
**Cl > F > S > O**