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Dalton
Dalton believed that all substances are made of atoms, and that atoms can't be created, divided, or destroyed. He also believed that atoms of the same element are exactly alike and that atoms can join to make new atoms. -
Thomson
Thomson disconvered that there were small particles inside atoms, and that atoms could be divided. Thomson also discovered electrons, and made the connection that electrons are all throughout an atom like plums are in plum pudding. -
Rutherford (1909)
Rutherford wanted to test Thomson's theory so he aimed a beam of positively charged particles at gold foil with special coating in a semi-cirble around it to trace where the beam of particles went. He found that some went straight through, some bounced to the side, and some bounced directly backwards. -
Rutherford (1911)
In 1911 Rutherford revised the Atomic Theory saying that in the center of the atom there is a small, very dense, and positive, part that he named a nucleus. He concluded that if a positive particle went too close to the nucleus it would be pushed back. -
Bohr
Bohr studied how atoms react to light. He proposed that electrons move around the neucleus in specific paths, and that the electrons can jump from one path to another but not in between paths. Like rungs on a ladder, you can't step in between rungs. -
Schrodinger and Heisenberg
Erwin Schrodinger, an Austrian physicist and a German physicist Wener Heisenberg, explained that electrons don't travel in paths and that Bohr was wrong. They said that it is impossible to predict the exact path of electrons. -
Aristotle
Aristotle was a Greek philosepher who believed that you could never end up with a particle that couldn't be cut. -
Democritus
Democritus was a Greek philosepher that around 440 BC came up with the theory that you can't cut a particle in half forever. He believed that you would eventually end up with a particle that was small and hard, he called it an atom.
