I discovered the electron by performing experiments with a cathode ray and a magnet. I found that there were negative and positive charges in atoms. I called my model "Plum Pudding."
During my experiments I observed that the mass of an electron is smaller than Hydrogen, electrons deflect negative charge, and no matter what metal you put near the cathode ray, the same thing happens. So, the electron must be smaller than an atom, the electron must be negative, and all atoms must have electrons.
Atoms contain electrons and electrons are negatively charged. When I performed my experiments with the cathode ray, I found the putting a magnet over the ray caused it to bend away from the magnet.
I had a student named Ernest Rutherford who had worked with me before my discovery of the electron. I had invited him to work with me in my laboratory to study X-Rays when he was a student at the University of Cambridge. After this, I went on to discover the electron while he began his own experiments.
I discovered the positively-charged nucleus by shooting alpha particles (positively-charged particles) at gold foil and observing what would happen. I called this my "Gold Foil Experiment."
Discovered the nucleus using alpha particles.
Gold Foil Experiment
Most of the time, the alpha particles would just go right through the foil to the other side, but occasionally an alpha particle would bounce off the foil and come flying back towards me.
There is a positively charged nucleus in the center of the atom, and atoms are mostly empty space.
Since the alpha particles only bounce back occasionally, meaning most go right through the foil, then that tells us the nucleus has a positive charge and is very small, while most of the atom is made up of empty space.