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200
Aristotle
Aristotle strongly disagreed with Democritus on the development of atoms. He thought that there could never be a particle that could not be divided. Democritus, however was correct. -
Dalton
Dalton's theory stated that all particles are atome and atoms cannot be created, divided or destroyed. Also, atoms of the same element are alike, and atoms of different elements are different. Lastly, atoms join with other atoms to make new substances. -
Thomson
Thomson dsicovered that there are smaller particles inside of atoms, which was a revision to Dalton and the Greek theories. He named these particles electrons. -
Rutherford- 1909
Rutherford designed an experiment to test Thomson's theory. This experiment involved shooting atoms at a sheet of gold. The results were that some of the atoms were bounced back towards Rutherford. -
Rutherford 1911
Rutherford changed the atomic theory proposed by Thompson. He put a "neucleus" in the center of the atom with electrons circling around it. They moved because they contained different charges and were attracted or repelled. -
Bohr
Bohr's studies about the way atoms react to light. The results of this study led him to believe that electrons circle around the nucleus in specific patterns. He said that the atom was like a ladder and the electrons cannot go between the rungs. -
Schrodinger and Heisenberg- during the 20th century
These scientists explained that electrons don't travel in specific paths like Bohr suggested. They said that in actuality, the paths of electrons are hard to locate and that rather, they can be found in electron clouds. -
Period: to
The Devolpment of Atomic Theory
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Democritus- 440 BC
A Greek philosipher named Democritus predicted that eventually there would be a particle of matter too small to split. He called the new type of particle the "atom". He said the atom would be hard and small.
