For magnitude of electron gain enthalpy of chalcogens and halogens, which of the following option is correct?

Options

A. `Br gt F`
B. `S gt F`
C. `O lt Cl`
D. `S lt Se`

Explanation

To determine the correct order of electron gain enthalpy for chalcogens and halogens, we need to analyze the trends in the periodic table. Here’s a step-by-step solution:

### Step 1: Identify the Groups
Chalcogens are in Group 16 of the periodic table, which includes Oxygen (O), Sulfur (S), Selenium (Se), and Tellurium (Te). Halogens are in Group 17, which includes Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I).

### Step 2: Understand the Trend of Electron Gain Enthalpy
- **Left to Right**: As we move from left to right across a period, the electron gain enthalpy generally increases. This is due to the increasing nuclear charge, which attracts the incoming electron more strongly.
- **Top to Bottom**: As we move down a group, the electron gain enthalpy generally decreases. This is due to the increase in atomic size and the corresponding increase in distance between the nucleus and the incoming electron, which reduces the attraction.

### Step 3: Analyze Specific Elements
- For **Chalcogens**:
- Oxygen has the lowest electron gain enthalpy in its group due to high inter-electronic repulsion in its small size.
- Sulfur, being larger, has a higher electron gain enthalpy than Oxygen.
- Selenium has a higher electron gain enthalpy than Sulfur.

- For **Halogens**:
- Fluorine has a lower electron gain enthalpy than Chlorine because of its small size causing greater inter-electronic repulsion.
- Chlorine has a higher electron gain enthalpy than Fluorine.
- Bromine has a lower electron gain enthalpy than Chlorine.

### Step 4: Establish the Order
From the analysis:
- The order of electron gain enthalpy from highest to lowest is:
- Cl > F > S > O > Br > Se

### Step 5: Evaluate the Options
1. **Bromine's Electron Gain Enthalpy is greater than Fluorine**: Incorrect.
2. **Sulfur's Electron Gain Enthalpy is greater than Fluorine**: Incorrect.
3. **Chlorine's Electron Gain Enthalpy is greater than Oxygen**: Correct.
4. **Selenium's Electron Gain Enthalpy is greater than Sulfur**: Incorrect.

### Conclusion
The correct option is that Chlorine's electron gain enthalpy is greater than Oxygen.

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