The correct order of electron gain enthalpy is

Options

A. `SgtSegtTegtO`
B. `TegtSegtSgtO`
C. `OgtSgtSegtTe`
D. `SgtOgtSegtTe`

Answer

To determine the correct order of electron gain enthalpy for the elements oxygen (O), sulfur (S), selenium (Se), and tellurium (Te), we can analyze the trends in the periodic table and the specific values of electron gain enthalpy for these elements.

### Step-by-Step Solution:

1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy is defined as the amount of energy released when an electron is added to an isolated gaseous atom. A more negative value indicates a greater tendency to gain an electron.

2. **Identifying the Elements and Their Positions**:
- The elements in question are oxygen (O), sulfur (S), selenium (Se), and tellurium (Te). These elements belong to Group 16 of the periodic table.

3. **Reviewing the Electron Gain Enthalpy Values**:
- The electron gain enthalpy values (in kilojoules per mole) for the elements are as follows:
- Oxygen (O): -141 kJ/mol
- Sulfur (S): -195 kJ/mol
- Selenium (Se): -200 kJ/mol
- Tellurium (Te): -190 kJ/mol

4. **Analyzing the Trends**:
- As we move down the group from oxygen to tellurium, the atomic size increases. This increase in size generally leads to a decrease in the electron gain enthalpy because the added electron experiences less effective nuclear charge.
- However, oxygen has a smaller size and higher electron density, making it less favorable to add an electron compared to sulfur, selenium, and tellurium.

5. **Determining the Correct Order**:
- Based on the values:
- Sulfur (-195) has a more negative value than oxygen (-141), indicating it has a higher electron gain enthalpy.
- Selenium (-200) is more negative than sulfur (-195).
- Tellurium (-190) is less negative than selenium but more negative than oxygen.
- Therefore, the correct order of electron gain enthalpy from most negative to least negative is:
- **Selenium (Se) > Sulfur (S) > Tellurium (Te) > Oxygen (O)**.

### Final Answer:
The correct order of electron gain enthalpy is: **Se > S > Te > O**.