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200
Democritus 440 B.C
Democritus was a Greek philosopher who thought that thers was a particle that could not be cut. He called this particle an atom. -
200
Aristotle
Aristole said the you could never have a particle that could never be cut, he had people think he was right. Demo said an atom is the smallest particle into which an element can be divided and still be the same substance. -
Period: 200 to
The Development of Atomic Theroy
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John Dalton
John Dalton, a British chemist and a school teacher, published his atomic theory in 1803. All substances are made of atoms. Atoms are small particle that cannot be created, divided or destroyed. -
J.J Thompson
J.J Thomson, a British scientist, discovered that there are small particles inside the atom, which means that atoms can be divded into even smaller paritcles. He thought that the electrons were mixed throught the nucleus. -
Ernest Rutheford
Ernest Ruthserford thought that atoms are soft blobs of matter. He expanded the particles to pass roght though the gold in a straight line, but some of the particles were defleted. some even bounced straight back. -
Ernest Rutherford
Rutherford proposed in 1911 that in the center of an atom there is a tiny , extremely dense, postively charged part called the nucleus. The charges repel. Rutherford reasoned that positively charged particles that went by would be pushed back straight from were they came from. -
Niels Bohr
Niels Bohr studied the way that atoms react to light. Bohr's results led him to the propose that electrons move around the nucles in certain paths, or energy levels. In Bohr's model there are no paths between levels. Electrons can jump from one path in another level to another path in another level. -
Schrodinger and Heisenberg
Schrodinger and Heisenberg said that electrons do not travel in definite paths and the path canot be predicted. They proposed regions in the atoms called electron clouds.
