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440 BCE
Democritus
Atoms are "incuttable."
Atoms constantly move
Atoms are small, hard particles -
440 BCE
Democritus Atomic Model
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Period: 440 BCE to
Atomic Theory Timeline
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John Dalton
All substances are made of atoms. Atoms of different elements are different. Atoms of the same elements are exactly the same. Elements combine in specific proportions. He conducted experiments in combining elements. -
John Dalton Atomic Model
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J.J. Thomson
He conducted the cathode-ray tube experiment. His theory of the atomic structure lead to the "plum-pudding" model. There are small, negatively charged particles inside an atom. -
J.J. Thomson Atomic Model
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Ernest Rutherford
Atoms contain mostly empty space. He conducted the gold foil experiment. Most of an atom's mass is in the nucleus. There is a small, dense, positively charged nucleus. Electrons move in empty space in the atom. -
Ernest Rutherford Atomic Model
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Niels Bohr
Electrons jump between levels from path to path. Electrons travel in definite paths. -
Niels Bohr Atomic Model
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Erwin Schrodinger and Werner Heisenberg
Electron paths cannot be predicted. Electrons are found in electron clouds, not paths. -
Erwin Schrodinger and Werner Heisenberg Atomic Model
