For the symbol H, D and T ; tabulate three sub- atomic particles found in each of them.

Hint: We know that the mass number of an element is the sum of the number of protons and neutrons. All these are isotopes, so they will have the same atomic number but a different mass number. The sub atomic particles can be calculated from the calculations of mass number and atomic number.

Complete answer:
First, let us know what the mass number is. The mass number can be defined as the sum of the number of protons and neutrons. As protons and neutrons, both are present in the nucleus of an atom. So, the mass number can also be called as the total number of nucleons present. Now, let us see what subatomic particles are. The protons, neutrons and the electrons are called subatomic particles because it is believed that the atom consists of protons and neutrons in the centre forming nucleus and electrons revolving around them.
The ‘H’ is a hydrogen atom that consists of one proton and one electron.
The ‘D’ is deuterium which is an isotope of hydrogen. It consists of mass number 2 but the atomic number is 1. It has one proton, one neutron and one electron.
The ‘T’ is Tritium which is also an isotope of hydrogen and deuterium. It has mass number 3 and atomic number 1. It consists of one proton, two neutrons and one electron.

Note: The isotopes are those atoms that have atomic numbers but the mass number is different. The H, D and T are isotopes of the element hydrogen. The atomic number of an element is equal to the number of protons or the number of electrons in a neutral atom.