Another answer for losing electrons is donating because if you accept you have more and therefore it’s donating because you give some away
The main difference between the 3 isotopes of hydrogen are the number of neutrons in the nucleus. Hydrogen has no neutrons, Deuterium has one neutron, and tritium has two neutrons. All three have one proton and one electron.
In a model, the particles are not the actual size. They are just representing the gas particles. In a gas, the particles are smaller and in their own material