The appreciable radioactivity of uranium minerals is mainly due to:

Options

A. An uranium isotope of mass number 235
B. A thorium isotope of mass number 232
C. Actinium
D. Radium

Answer

To solve the question regarding the appreciable radioactivity of uranium minerals, we will analyze the options provided and determine which element contributes most significantly to the radioactivity.

### Step-by-Step Solution:

1. **Understanding Radioactivity**:
- Radioactivity is the process by which unstable atomic nuclei lose energy by emitting radiation. This can occur in various isotopes of elements.

2. **Analyzing the Options**:
- The options given are:
1. Uranium isotope with mass number 235
2. Thorium isotope with mass number 232
3. Titanium
4. Radium

3. **Comparing the Radioactivity of Each Element**:
- **Uranium-235**: This isotope is known for its use in nuclear reactors and weapons, but it is not the most radioactive.
- **Thorium-232**: While thorium is radioactive, it is less so compared to radium.
- **Titanium**: Titanium is not radioactive and does not contribute to the radioactivity of uranium minerals.
- **Radium**: Radium is known to be highly radioactive and is often associated with uranium minerals due to its decay products.

4. **Conclusion**:
- Among the options, radium is the most radioactive element. Therefore, the appreciable radioactivity of uranium minerals is mainly due to the presence of radium.

5. **Final Answer**:
- The correct answer is **Radium** (Option 4).