Proton

A proton is an elementary particle that is the positive unit charged constituent of ordinary matter. Its mass is 938 MeV and has a spin of 1/2. Protons are one of the particles constituting all nuclei. It is currently believed that protons do not decay although experiments are going on to prove that they do have a half life of approximately 10³⁰ years. It is believed that most of the matter in the universe is in the form of protons.