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370 BCE
Democritus
Democritus discovered the atom. The experiment that he did to discover this involved him taking a sea shell and braking it in half again and again until he was left with a powder substance, he then tried to break the powder but was unsuccessful and concluded that everything is made of atoms. -
John dalton
He proposed the theory that elements differed due to the mass of the atoms. He did many experiments to come to this conclusion. One was the law of conservation of mass the total mass of chemicals does not change in a chemical reaction. And the law of definite proportion to form compounds, elements combine in certain proportions by mass. And many more -
J.J Thompson
He discovered the electron by experimenting with a cathode ray tube. He showed that cathode rays were negatively charged. And he also discovered that the model of the atom was wrong so he purposed a new model that was like bread pudding -
Joseph Rutherford
Ernest Rutherford proved pudding structure incorrect. He did a experiment using alpha particles. He aimed alpha particles at gold foil and recorded the location of the alpha particle strikes on screen as they passed through .most of the alpha particles passed unaffected through the gold foil as expected, a small number of particles were deflected at an angle, and a few ricocheted straight back. Rutherford concluded that the atom consisted of a small, dense, positively charged nucleus. -
Bohr
He produced the theory of quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted
