Which of the following has magic number of neutrons?

Options

A. `._(13)Al^(27)`
B. `._(83)Bi^(209)`
C. `._(92)U^(238)`
D. `._(26)Fe^(56)`

Answer

To determine which of the given options has a magic number of neutrons, we will follow these steps:

### Step 1: Understand the concept of magic numbers
Magic numbers of neutrons are specific numbers that correspond to stable configurations in atomic nuclei. The known magic numbers are 2, 8, 20, 28, 50, 82, and 126.

### Step 2: Calculate the number of neutrons for each option
We will calculate the number of neutrons using the formula:
\[ \text{Number of neutrons} = \text{Mass number} - \text{Atomic number} \]

### Step 3: Analyze each option

**Option A: Aluminium (Al)**
- Mass number = 27
- Atomic number = 13
- Number of neutrons = 27 - 13 = 14
- **14 is not a magic number.**

**Option B: Bismuth (Bi)**
- Mass number = 209
- Atomic number = 83
- Number of neutrons = 209 - 83 = 126
- **126 is a magic number.**

**Option C: Uranium (U)**
- Mass number = 238
- Atomic number = 92
- Number of neutrons = 238 - 92 = 146
- **146 is not a magic number.**

**Option D: Iron (Fe)**
- Mass number = 56
- Atomic number = 26
- Number of neutrons = 56 - 26 = 30
- **30 is not a magic number.**

### Step 4: Conclusion
From the calculations, only Bismuth (Bi) has a magic number of neutrons, which is 126.

### Final Answer:
**Option B: Bismuth (Bi)** has a magic number of neutrons.

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