The work of J.J Thomson’s student, Ernest Rutherford, led to the discovery of the Proton. Working with alpha particles fired at a piece of gold foil it was observed that instead of passing straight through it was scattered. Suggesting there was something large in the centre of the atom.
Wave Particle Duality was a revolutionary way of treating electrons as not just particles but also as waves at the same time. This opened up new doors in the explanation of the atom and its behaviours influencing the field of Quantum Mechanics.