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440 BCE
Democritus
Atoms are "uncut-able"
Atoms are small, hard particles
Atoms constantly move -
Period: 440 BCE to
Atomic Theory Timeline
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440
Democratus Atom Model
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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 alike
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
Electrons move in empty space in the atom
He conducted the gold foil experiment
Most of an atom's mass is in the nucleus
there is a small, dense, positively charged nucleus -
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 Theory
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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 Atom Model
