-
440 BCE
Democritus
Said atoms are "ucncuttable". Atoms are small, hard particles. All substances are made of atoms. Atoms constantly move. -
440 BCE
Democritus
Atomic Model -
John Dalton
Atoms of different elements are different. Atoms of the same element are exactly alike. Elements combine in specific proportions. Conducted experiments in combining elements. -
John Dalton
-
J.J. Thomson
There are small, negatively charged particles inside and atom. His theory lead to the "plum-pudding" model. Conducted the cathode-ray experiment. -
J. J. Thomson
-
Ernest Rutherford
Conducted gold foil experiment. There is a small, dense, positively charged nucleus. Most of an atom's mass is in the nucleus. Electrons move in empty space in the atom. -
Ernest Rutherford
-
Niels Bohr
Believed electrons jumped between levels from path to path. Electrons travel in definite paths. -
Niels Bohr
-
Schrodinger and Heisenberg
Believed electron paths can not be predicted. Electrons are found in electron clouds, not paths. -
Schrodinger and Heisenberg
