Question

Do protons, neutrons or electrons have the smallest mass?

Answer 1

I think what your asking is whether or not you can get smaller masses than an electron, proton or neutron. The answer is yes.

Explanation:

Protons, neutrons and electrons are sub-atomic particles. Electrons actually behave as waves as well as particles but do still have a mass (it is just very small compared to a proton or neutron).

Einsteins equation `E=mc^2` tells us that Energy is equal to the mass of a particle times the speed of light (squared). Therefore, all particles (even a photon) can exhibit energy which can be considered mass - but this does not mean a photon actually HAS mass, it just exhibits energy that can be considered as mass when the photon is moving. A photon, however, is not considered to have a mass at 'rest'. I.e. you couldn't weigh (theoretically...) a photon to get a mass.

The smallest particles to have a 'mass' as we conventionally think of a mass are neutrinos. There is some debate as to whether they have a mass, but recent data suggests they do. It is just VERY small. Neutrinos are intact incredibly common but just incredibly hard to detect because they have very little interaction with matter.