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400 BCE
Democritus
Democritus took a seashell and kept breaking them into halves till they became dust, he then took the smallest piece if the dust and tried to break it more, but failed to. This lead to the discovery of the atoms being the building blocks of life -
John Dalton
He made the atomic theory. He believed that atoms of different elements could be distinguished universally by how much they weighed. Also discovered that atoms cannot be created nor destroyed. -
J. J. Thomson
Discovered a method to separate different types of atoms and molecules of positive rays. He also discovered electrons using cathode rays. He noted that one can divide an atom. Also discovered that atoms have a positive center with negative particles. -
Niels Bohr
Theorized that electrons orbit and had fixed placing a around the nucleus like planets that orbit the sun. Rutherford being a student of his, discovered it. He and Rutherford have the model named both after them, mostly common as the Bohr-Model -
Ernest Rutherford
Made a atomic model that had the protons in the center. He said that the majority of the weight in an atom was concentrated within the center and that the electrons floated around like how the planets orbit the sun. He discovered alpha particles using gold foil; he found them by shooting them at the foil and saw that they went through.
