-
400 BCE
Democritus
-Atoms are small, hard particles
-Atoms constantly move -
400 BCE
Democritus' Model
Democritus -
John Dalton
-All substances are made of atoms
-Atoms are "uncuttable"
-Atoms of different elements are different
-Atoms of the same element are exactly alike
-Elements combine in specific proportions
-Conducted experiments in combining elements -
Billiard Ball Model
John Dalton -
J.J. Thomson
-Conducted the Cathode-Ray tube experiment
-Theory of the atomic structure leads to the "plum-pudding" model
-There are small, negatively charged particles inside an atom -
Plum Pudding Model
J.J. Thomson -
Ernest Rutherford
-Atoms contain mostly empty space
-Conducted the gold foil experiment
-Most of an atom's mass is in the nucleus
-There is a small, dense, positively charged nucleus -
Nuclear Model
Ernest Rutherford -
Niels Bohr
-Electrons jump between levels from path to path
-Electrons move in empty space in the atom
-Electrons travel in definite paths -
Planetary Model
Niels Bohr -
Erwin Schrödinger
-Electrons paths cannot be predicted
-Electrons are found in electron clouds, not paths -
Werner Heisenberg
-Electrons are found in electron clouds, not paths -
Quantum Mechanical Model
Erwin Schrodinger and Werner Heisenberg
