Explanation

Hydrogen is the lightest element, and its most common isotope (protium) has no neutrons in its atomic nucleus.

The atomic number of hydrogen is 1, which means it has one proton in its nucleus, but no neutrons.

The three main isotopes of hydrogen:

• Protium (1H): 1 proton, 0 neutrons
• Deuterium (2H or D): 1 proton, 1 neutron
• Tritium (3H or T): 1 proton, 2 neutrons