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400
Democritus (400)
After he heard a chat, he believed there had to be a building block that had up all matter Duignan, Brian. "Democritus | Biography - Greek Philosopher." Encyclopedia Britannica Online. Encyclopedia Britannica, 2015. Web. 20 Feb. 2015 -
Period: 400 to
History of the Atom Timeline
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dalton(1803)
Dalton discovered there were many differernt kinds of atoms. He spnt time in his lab observing chemical reactions. He thought atoms were tiny indestructible particles, he called his model the Billiard Ball mode.
Brown, Eric. "Dalton Atom | Search Results | Educational Technology." Educational Technology. Eric Brown, 2007. Web. 25 Feb. 2015 -
Thomson (1897)
He discovered it had positive and negative charges. He discovered the electron in a series of experimennts designed to study the nature of electric discharge in a high vaccumcathode ray tube. He thought the atom was a sphere with positive charges throughout it and negatively charged particles were also scattered across his model. -
Rutherford (1911)
he discovered protons in the nucleus and the elctrons orbited around the nucleus like planets around the sun. He did the gold foil experiment in which he demonstrated that the atom has a tiny, heavy nucleus. He thought the atom had a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom and with the central volume also containing the bulk of the atomic mass ofDeleon, N. "Rutherford Model of the Atom." Rutherford Model of the Atom. N. the atom. -
Bohr (1913)
He propose that energy levels of electrons are discrete and that the electrons revolve instable orbits around the atomic nucleus but can jump from one energy level to another. He used theories from observations. He thought the nucleus occupied a dense central region and the electrons orbit the nucleus at discrete distances much like planets orbiting the sun. -
Heisenberg and Schrodiner (1925 - 1927)
They discovered electrons do not travel in efinate paths around the nucleus and electron clouds. They did experiments. They thought the nucelus surounded by distribution probabilities of electrons.http://www.aip.org/history/heisenberg/p01.htm
