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440 BCE
Democritus
Atoms are "uncuttable"
Atoms are small, hard particles
Atoms constantly move -
John Dalton
All substances are made of atoms, atoms of different elements are different, atoms of the same element are exactly alike, elements combine in specific proportions, conducted experiments in combining elements -
J.J. Thomas
Conducted the cathode-ray tube experiment, his theory was of the atomic structure lead to the "plum-pudding" model, there are small negatively charged particles inside the atom -
Ernest Rutherford
Atoms contain mostly empty space, electrons move in empty space in the atom, conducted the gold foil experiment, most of an atoms mass is in the nucleus, there is a small dense, positively charged nucleus -
Niels Bohr
Electrons jump between levels from path to path, electrons travel in definite paths -
Erwin Schrodinger and Werner Heisenberg
Electron paths cannot be predicted, electrons are found in electron clouds not paths
