Deuterium is an isotope of hydrogen. How many neutrons does it contain?

Options

A. 1
B. 0
C. 2
D. 3

Explanation

To determine how many neutrons are in deuterium, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Isotopes**:
- Isotopes are atoms of the same element that have the same atomic number but different mass numbers. This means they have the same number of protons but a different number of neutrons.

2. **Identify Deuterium**:
- Deuterium is one of the isotopes of hydrogen. The three isotopes of hydrogen are:
- **Protium** (mass number 1)
- **Deuterium** (mass number 2)
- **Tritium** (mass number 3)

3. **Know the Atomic Number of Hydrogen**:
- The atomic number (Z) of hydrogen is 1. This means that hydrogen (and all its isotopes) has 1 proton.

4. **Determine the Mass Number of Deuterium**:
- The mass number (A) of deuterium is 2.

5. **Use the Formula to Find Neutrons**:
- The number of neutrons (N) can be calculated using the formula:
\[ N = A - Z \]
- Here, A is the mass number and Z is the atomic number.

6. **Calculate Neutrons in Deuterium**:
- Substitute the values for deuterium:
\[ N = 2 - 1 = 1 \]
- Therefore, deuterium contains 1 neutron.

### Final Answer:
Deuterium contains **1 neutron**.

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