The number of neutrons present in the deuterium isotope of hydrogen is

Options

A. 2
B. 3
C. 5
D. 1

Answer

To find the number of neutrons in the deuterium isotope of hydrogen, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Isotope**:
- Deuterium is one of the isotopes of hydrogen. It is represented as \( ^2_1H \), where the superscript (2) indicates the atomic mass (mass number) and the subscript (1) indicates the atomic number.

2. **Understand Atomic Number and Mass Number**:
- The atomic number (Z) of deuterium is 1, which means it has 1 proton.
- The mass number (A) of deuterium is 2.

3. **Use the Formula for Mass Number**:
- The mass number (A) is the sum of the number of protons (P) and the number of neutrons (N). This can be expressed as:
\[ A = P + N \]

4. **Substitute Known Values**:
- We know from the previous steps that:
- \( A = 2 \) (mass number of deuterium)
- \( P = 1 \) (number of protons in deuterium)
- Substitute these values into the formula:
\[ 2 = 1 + N \]

5. **Solve for Neutrons (N)**:
- Rearranging the equation gives:
\[ N = 2 - 1 \]
- Therefore:
\[ N = 1 \]

6. **Conclusion**:
- The number of neutrons present in the deuterium isotope of hydrogen is **1**.

### Final Answer:
The number of neutrons present in the deuterium isotope of hydrogen is **1**.