Where are the protons and `O_(2)`, formed during splitting of water, likely to be released.

Answer

To answer the question "Where are the protons and O₂ formed during the splitting of water likely to be released?", we can break down the process as follows:

### Step-by-Step Solution:

1. **Understanding Water Splitting in Photosynthesis**:
- During photosynthesis, specifically in the light-dependent reactions, water (H₂O) is split into protons (H⁺ ions) and oxygen (O₂) molecules. This process is known as photolysis of water.

2. **Location of Water Splitting**:
- The splitting of water occurs in the thylakoid membranes of the chloroplasts. These membranes are essential for the light-dependent reactions of photosynthesis.

3. **Release of Protons (H⁺)**:
- The protons (H⁺ ions) produced during the splitting of water are released into the thylakoid lumen (the internal space of the thylakoid). This accumulation of protons is crucial for creating a proton gradient that drives ATP synthesis.

4. **Release of Oxygen (O₂)**:
- The oxygen produced during the photolysis of water is released into the atmosphere. This oxygen comes from the water molecules that are split, and it exits the thylakoid membrane into the surrounding environment.

5. **Summary of Releases**:
- Therefore, the protons are released into the thylakoid lumen, and the oxygen is released outside of the thylakoid membrane into the atmosphere.

### Final Answer:
- Protons (H⁺) are released in the thylakoid lumen, and oxygen (O₂) is released outside of the thylakoid membrane.