Which of the following is artificial radioactive series?

Options

A. `4n + 1`
B. `4n + 2`
C. `4n`
D. `4n + 3`

Explanation

To determine which of the following is an artificial radioactive series, we can analyze the options provided.

### Step-by-Step Solution:

1. **Understand Radioactive Series**:
- Radioactive series can be classified as natural or artificial. Natural series consist of isotopes that occur in nature, while artificial series are man-made and do not occur naturally.

2. **Identify the Series**:
- The question mentions different series: 4n, 4n + 1, 4n + 2, and 4n + 3 series. We need to identify which of these is artificial.

3. **Analyze the 4n + 1 Series**:
- The 4n + 1 series is known as the Neptunium series. This series starts with Neptunium-237 (Np-237) and ends with Bismuth-209 (Bi-209).

4. **Characteristics of the Neptunium Series**:
- The Neptunium series is characterized by the emission of 8 alpha particles and 5 beta particles during its decay process.
- It is important to note that the elements in this series are not found in nature, confirming that it is indeed an artificial series.

5. **Conclusion**:
- Based on the analysis, the 4n + 1 series (Neptunium series) is the artificial radioactive series.

### Final Answer:
The artificial radioactive series is the **4n + 1 series (Neptunium series)**.