The increasing order of electron affinity values of `O,S` and `Se` is

Options

A. `O gt S gt Se`
B. `S gt Se gt O`
C. `Se gt O gt S`
D. `Se gt S gt O`

Answer

To determine the increasing order of electron affinity values for oxygen (O), sulfur (S), and selenium (Se), we need to consider the concepts of atomic size, electronegativity, and the general trends in the periodic table.

### Step-by-Step Solution:

1. **Understanding Electron Affinity**:
- Electron affinity is defined as the amount of energy released when a gaseous atom accepts an electron to form an anion. Higher electron affinity values indicate a greater tendency to gain an electron.

2. **Position in the Periodic Table**:
- Oxygen (O), sulfur (S), and selenium (Se) are all in Group 16 of the periodic table. As we move down the group from oxygen to selenium, the atomic size increases.

3. **Trends in Electron Affinity**:
- Generally, as we move down a group in the periodic table, the electron affinity decreases. This is because the increased distance between the nucleus and the added electron reduces the attraction, making it less favorable for the atom to gain an electron.

4. **Comparing Oxygen, Sulfur, and Selenium**:
- Oxygen is smaller in size and has a high electronegativity, which means it has a strong attraction for electrons. However, due to its small size, the added electron experiences significant repulsion from the electrons already present, leading to a lower electron affinity than expected.
- Sulfur, being larger than oxygen, has a lower electronegativity and thus a higher electron affinity compared to oxygen.
- Selenium, being even larger than sulfur, has the lowest electron affinity among the three.

5. **Conclusion**:
- Based on the above analysis, the increasing order of electron affinity values is:
\[ \text{O} < \text{S} < \text{Se} \]

### Final Answer:
The increasing order of electron affinity values of O, S, and Se is:
\[ \text{O} < \text{S} < \text{Se} \]