Choose the element which is not radioactive

Options

A. Cm
B. No
C. Mo
D. Md

Answer

To determine which element is not radioactive, we need to understand the concept of radioactivity and the atomic numbers of the elements provided in the options.

### Step-by-Step Solution:

1. **Understand Radioactivity**:
- Radioactive elements are those that have unstable nuclei and emit radiation. Generally, elements with atomic numbers greater than 82 (lead) are considered radioactive.

2. **List the Options**:
- Option 1: Curium (Cm) - Atomic number 96
- Option 2: Nobilium (No) - Atomic number 102
- Option 3: Molybdenum (Mo) - Atomic number 42
- Option 4: Mendelevium (Md) - Atomic number 101

3. **Analyze Each Option**:
- **Curium (Cm)**: Atomic number 96, which is greater than 82. Therefore, it is radioactive.
- **Nobilium (No)**: Atomic number 102, which is also greater than 82. Thus, it is radioactive.
- **Molybdenum (Mo)**: Atomic number 42, which is less than 82. Therefore, it is not radioactive.
- **Mendelevium (Md)**: Atomic number 101, which is greater than 82. Hence, it is radioactive.

4. **Conclusion**:
- The only element from the options that is not radioactive is **Molybdenum (Mo)**.

### Final Answer:
The element which is not radioactive is **Molybdenum (Mo)**.