The number of neutrons in the element Be is

Options

A. 4
B. 5
C. 9
D. 13

Explanation

To find the number of neutrons in the element Beryllium (Be), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number and Atomic Mass**:
- The atomic number of Beryllium (Be) is 4. This means that Beryllium has 4 protons.
- The atomic mass of Beryllium is 9.

2. **Understand the Relationship**:
- The atomic mass (also known as mass number) is the sum of the number of protons and neutrons in an atom.
- The formula to find the number of neutrons is:
\[ \text{Number of Neutrons} = \text{Atomic Mass} - \text{Atomic Number} \]

3. **Substitute the Values**:
- Using the values we have:
\[ \text{Number of Neutrons} = 9 - 4 \]

4. **Calculate the Number of Neutrons**:
- Performing the subtraction:
\[ \text{Number of Neutrons} = 5 \]

5. **Conclusion**:
- Therefore, the number of neutrons in the element Beryllium (Be) is 5.

### Final Answer:
The number of neutrons in Beryllium (Be) is **5**.