Question

Of the 3 particles that make up most atoms there is one particle that doesn't appear in some hydrogen items what is it

Answer 1

The particle you are referring to is the neutron. Most hydrogen atoms consist of just one proton and one electron. However, there is an isotope of hydrogen known as protium that contains no neutrons; it has only one proton. The other isotopes of hydrogen, such as deuterium (which has one proton and one neutron) and tritium (which has one proton and two neutrons), do include neutrons. In summary, the neutron is the particle that is absent in the most common form of hydrogen, known as protium.