Which of the following processes is endothermic?

Options

A. `S to S^(-)`
B. `S^(-) to S^(2-)`
C. `Na to Na^(-)`
D. `P to P^(-)`

Answer

To determine which of the given processes is endothermic, we need to analyze each option based on the concept of energy changes during the processes.

### Step-by-Step Solution:

1. **Understanding Endothermic Processes**:
- An endothermic process is one that absorbs heat from the surroundings. This means that energy is required for the process to occur.

2. **Analyzing Electron Affinity**:
- Electron affinity is the energy change that occurs when an electron is added to a neutral atom. Typically, when an electron is added, energy is released, making it an exothermic process.

3. **Evaluating the Given Processes**:
- **Process 1**: Adding an electron to sulfur (S) - This is an exothermic process because energy is released when an electron is added to a neutral sulfur atom.
- **Process 2**: Adding an electron to sodium (Na) - Similar to sulfur, this is also an exothermic process as energy is released.
- **Process 3**: Adding an electron to phosphorus (P) - This process is exothermic as well since energy is released when an electron is added to phosphorus.
- **Process 4**: Converting sulfur anion (S⁻) to sulfur dianion (S²⁻) - In this case, sulfur already has one extra electron. Adding another electron will lead to electron-electron repulsion due to the negative charges. To overcome this repulsion, energy must be supplied, making this process endothermic.

4. **Conclusion**:
- The only endothermic process among the options is the conversion of sulfur anion (S⁻) to sulfur dianion (S²⁻). Therefore, the correct answer is that this process is endothermic.

### Final Answer:
The endothermic process is the conversion of sulfur anion (S⁻) to sulfur dianion (S²⁻).

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