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