Which of these is not regarded as a magic number

Options

A. 20
B. 50
C. 126
D. 6

Answer

To determine which of the given options is not regarded as a magic number, we need to understand what a magic number is in the context of nuclear chemistry.

### Step-by-Step Solution:

1. **Define Magic Number**:
- A magic number refers to the number of nucleons (protons and neutrons) in an atomic nucleus that are arranged in complete shells. This arrangement leads to increased stability of the nucleus.

2. **List Conventional Magic Numbers**:
- The conventional magic numbers are: 2, 8, 20, 28, 50, 82, and 126. These numbers indicate the number of protons or neutrons that result in a particularly stable nucleus.

3. **Analyze the Given Options**:
- We need to identify which number from the options provided is not included in the list of conventional magic numbers.

4. **Evaluate Each Option**:
- If the options include numbers like 2, 8, 20, 28, 50, 82, or 126, they are regarded as magic numbers.
- If any option includes a number such as 6, it is not a magic number according to the conventional list.

5. **Conclusion**:
- Based on the analysis, the number 6 is not regarded as a magic number.

### Final Answer:
The number that is not regarded as a magic number is **6**.

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