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460 BCE
Democritus
He was a Greek philosopher who developed/introduced the theory that atoms were invisible and indestructible. Democritus is considered a philosopher because he did not record any or his data. Democritus's atomic model is a sphere. -
John Dalton
Formulated the law of particle pressure. Concluded that all elements were made or invisible particles, atoms of the same element are identical, atoms of different elements have different structures, atoms can mix physically and chemically, and that atoms of one element are never changed into another. Daltons model was a sphere -
Eugen Goldstein
Discovered evidence of protons (positively charged particles) he observed rays going the opposite way in a cathode ray tube, because cathode rays were believed to be negative he assumed that the rays going the opposite way were positive. Goldstein's model adds the presence of positively charged particles. -
J.J. Thomson
Found evidence of negative charges in atoms. Found using experiments that involved a cathode ray. Thomson's model is the plum pudding model that shows the atom as a positive sphere with negative atoms spread throughout. -
Robert Millikan
His contribution to the atomic theory was deducing the electric charge of an electron. This discovery was made from his famous Oil-Drop experiment. In this experiment, he used oil instead of water in his atomizer. He then had it fall down in between two charged plates and observed the charge of the oils. -
Earnest Rutherford
Discovered or found evidence of the atomic nucleus using the gold foil experiment. He concluded that all particle in the nucleus were positively charged. in Rutherford's model, the negative parts of the atom float around the positive nucleus within the atom. -
Neil Bohr
Neil Bohr’s Atomic theory says that an atom is like a planetary model where electrons were situated in discretely energized orbits -
Erwin Schrodinger
Introduced the idea that electron particles float in a cloud around the nucleus of the atom
