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

Options

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

Answer

To determine the correct order of electron gain enthalpy for the given atomic species (Fluorine, Chlorine, Sulfur, and Oxygen), 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 an isolated gaseous atom. It is typically a negative value since energy is released during the process.

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

### Step 3: Analyze the Electron Configuration
- Group 16 elements have the general electronic configuration of ns²np⁴.
- Group 17 elements have the general electronic configuration of ns²np⁵.
- When these elements gain an electron, they achieve a noble gas configuration, which is more stable.

### Step 4: Compare Electron Gain Enthalpy of Halogens
- Fluorine has a smaller atomic radius compared to Chlorine, which means it has a higher nuclear charge relative to its size.
- However, due to the smaller size of Fluorine, the electron-electron repulsion when adding an electron is significant.
- Chlorine, being larger, has a lower electron-electron repulsion when gaining an electron, making it easier for Chlorine to gain an electron compared to Fluorine.

### Step 5: Compare Electron Gain Enthalpy of Chalcogens
- Oxygen has a smaller atomic radius compared to Sulfur, similar to the case with Fluorine and Chlorine.
- Oxygen's higher nuclear charge and smaller size lead to significant electron-electron repulsion when an electron is added.
- Sulfur, being larger, can accommodate more electrons with less repulsion, making it easier for Sulfur to gain an electron compared to Oxygen.

### Step 6: Establish the Order of Electron Gain Enthalpy
Based on the analysis:
1. Chlorine has the highest electron gain enthalpy due to lower repulsion compared to Fluorine.
2. Fluorine follows, as it has a high nuclear charge but experiences more repulsion.
3. Sulfur has a higher electron gain enthalpy than Oxygen due to lower repulsion.
4. Oxygen has the lowest electron gain enthalpy.

Thus, the correct order of electron gain enthalpy is:
**Cl > F > S > O**

### Final Answer
The correct arrangement representing the order of electron gain enthalpy for the given atomic species is:
**Chlorine (Cl) > Fluorine (F) > Sulfur (S) > Oxygen (O)**

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