Which of the following is energy releasing process ?

Options

A. `X^(-) to X (g) +e^(-)`
B. `O^(-)(g) +e^(-) to O^(2-)`
C. `O(g) to O^(+)(g) +e^(-)`
D. `O(g) +e^(-) to O^(-) (g)`

Explanation

To determine which of the following processes is energy-releasing, we need to analyze each option based on the concepts of ionization energy and electron affinity.

### Step-by-Step Solution:

1. **Understand Ionization Energy**:
- Ionization energy is the energy required to remove an electron from an atom or ion. This process is endothermic, meaning it absorbs energy.
- For example, if we have the process:
\[ X \rightarrow X^+ + e^- \]
Here, energy is absorbed to remove the electron, so this is not an energy-releasing process.

2. **Understand Electron Affinity**:
- Electron affinity is the energy change that occurs when an electron is added to a neutral atom. This can be either exothermic (releasing energy) or endothermic (absorbing energy), depending on the atom.
- For example, if we have the process:
\[ O^- + e^- \rightarrow O^{2-} \]
Here, the system gains an electron, and since the species already has a negative charge, energy is required for this process, making it endothermic.

3. **Analyze the Third Option**:
- Consider the process:
\[ O + e^- \rightarrow O^- \]
In this case, a neutral oxygen atom gains an electron. This is typically an exothermic process for many elements, meaning it releases energy. Thus, this is likely to be an energy-releasing process.

4. **Conclusion**:
- After analyzing all options, the process that releases energy is:
\[ O + e^- \rightarrow O^- \]
- Therefore, the correct answer is the process where a neutral oxygen atom accepts an electron.

### Final Answer:
The energy-releasing process is:
\[ O + e^- \rightarrow O^- \]