Notes

John Dalton - He had rediscovered the atom in 1808, and created a theory revolving around atoms called the Atomic Theory. This theory had 4 points: that all elements were made up of atoms, atoms of the same element are the same while atoms of different elements are different in some way, atoms of different elements combine to form compounds, and when compounds are made, atoms are neither created nor destroyed, but merely rearranged. Dalton also came up with the idea of the solid ball model, to show compounds.

Dimitri Mendeleev - Mendeleev created the first full periodic table in 1869, with open spaces for elements that hadn't been discovered yet at the time. He knew precisely where these unknown elements would go through family relationships.

JJ Thompson - Thompson discovered the electron in 1897, through the Cathode Ray Tube experiment. He discovered that an electric current was sent through the cathode-ray tube no matter what type of metal was at the ends of the cathode-ray tube. He proved that all atoms must contain electrons through this. In addition, Thompson found out that electrons were negatively charged particles from the ray in the cathode-ray tube coming from the negative electrode and it being pushed away from the negative pole of an electric field. Finally, he discovered the plum pudding model, with electrons being dispersed throughout the whole atom.

Ernest Rutherford - Rutherford discovered the nucleus in 1911 through his gold foil experiement. To prove JJ Thompson's Plum Pudding model, Rutherford set up an experiment that had alpha particles being shot at a sheet of gold foil with a barrier surrounding the gold foil to detect where the particles landed. When the particles were shot, most of them went straight through the gold foil and hit the barrier. But some of the alpha particles were deflected at large angles, hitting different sides of the barrier. And even some of the particles were reflected and did not hit the barrier. This proved that there was something in the atoms that made the particles not got straight through the gold foil. Rutherford explained this with the nuclear atom - an atom with a dense center that was positively charged, causing positive particles (which were the alpha particles) to bounce off of it. Rutherford disproved JJ Thompson's Plum Pudding Model and came up with a new model - the Planetary Model