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430 BCE
Democritus
He believed atoms were the smallest, "uncuttable" pieces of matter. -
Period: 430 BCE to
Atomic Theory History
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John Dalton
He believed that atoms of different elements were different, and atoms of the same elements were the same. All substances are made of atoms. -
J.J Thomson
There are small negatively charged atoms in an atom. He conducted the cathode ray experiment. He created the "plum pudding" model. -
Rutherford
He conducted the gold foil experiment. Atoms contain mostly open space. -
Bohr
Electrons travel in certain paths, or energy levels. He discovered neutrons, another kind of particle in the nucleus. Electrons can jump from a path in one level to a path in another. -
Shrodinger
Electron paths can not be predicted. -
James Chadwick
Most of an atom's mass is in the nucleus. Discovered the neutral neutron. There is a small dense positively charged nucleus. -
Heisenberg
Electrons are found in electron clouds not paths.
