jan 1, 1911 - Ernest Rutherford discovered the proton.

Description:

Rutherford and his collegues made an experiment that lead them to discover that atoms are mostly space, and that the majority of the mass is concentrated on the nucleous. He also discovered the proton, saying that there are sub atomic particles with positive charge surrounded by orbiting electrons with a negative charge.
This atomic model is known as the Quantum Model, and his experiment is called the Gold Foil experiment.