Tritium which is a radioactive isotope of hydrogen contains 1 proton and 1 neutron.

Explanation

### Step-by-Step Solution:

1. **Understanding 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. **Identifying Tritium**:
- Tritium is one of the isotopes of hydrogen. The elemental symbol for hydrogen is H. Hydrogen has three isotopes:
- Proteum (mass number 1)
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