To determine which element releases the largest amount of energy upon gaining an electron, we will analyze the electron gain enthalpy (or electron affinity) of the elements in question: Oxygen (O), Sulfur (S), Selenium (Se), and Tellurium (Te).
### Step-by-Step Solution:
1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy is the amount of energy released when an atom gains an electron. The more negative the value, the more energy is released, indicating a higher electron affinity.
2. **Identifying the Group**:
- The elements in question (O, S, Se, Te) belong to Group 16 of the periodic table, also known as the oxygen family.
3. **Trends in Electron Gain Enthalpy**:
- Generally, as we move down a group in the periodic table, the size of the atoms increases. This means that the outermost electrons are further from the nucleus, which can affect the attraction between the nucleus and the incoming electron.
4. **Comparing Sizes**:
- Oxygen is the smallest atom among the four, followed by Sulfur, Selenium, and Tellurium. The increasing atomic size leads to a decrease in the effective nuclear charge experienced by the outermost electrons.
5. **Inter-electronic Repulsion**:
- In smaller atoms like Oxygen, when an additional electron is added, there is significant inter-electronic repulsion between the incoming electron and the electrons already present. This repulsion can reduce the stability gained from adding the electron, resulting in a lower electron gain enthalpy.
6. **Actual Electron Gain Enthalpy Values**:
- Experimental data shows that the electron gain enthalpy values are as follows:
- Sulfur (S) has a higher electron gain enthalpy than Oxygen (O).
- The order of electron gain enthalpy is:
- Sulfur (S) > Oxygen (O) > Selenium (Se) > Tellurium (Te).
7. **Conclusion**:
- Therefore, the element that releases the largest amount of energy upon gaining an electron is **Sulfur (S)**.
### Final Answer:
**Sulfur (S) releases the largest amount of energy upon gaining an electron.**
