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400 BCE
Democtatus
Said that atoms are small particles, atoms are uncuttable, and atoms constantly move. Named atom "atomos" meaning "indivisible." -
John Dalton
Dalton said atoms of different elements are different, atoms join together with other atoms to make new substances, atoms of the same element are exactly alike, all substances are made of atoms, and elements combine in specific proportions. He also conducted experiments in combining elements. -
JJ Thompson
He conducted the cathode-ray tube experiment. He said there are small negatively charged particles inside an atom. His theory of the atomic structure led to the "plum pudding" or "chocolate chip cookie" model. -
Ernest Rutherford
He said there is a small, dense, positively charged nucleus. He also said Most of an atoms mass is in the nucleus and atoms contain mostly empty space. He conducted the gold foil experiment. -
Niels Bohr
Said electrons jump between levels from path to path, and electrons travel in definite paths. -
Schrodinger and Heisenberg
Schrodinger said Electron paths can not be predicted. He also said Electrons move in empty space in the atom. Schrodinger and Heisenberg both said Electrons are found in electron clouds, not paths. Schrodinger said this atomic model is known as the quantum mechanical model of the atom. He also used mathematical equations to describe the likelihood of finding an electron in a certain position.
