-
Period: 440 BCE to
Atomic Theory Timeline
-
440
Democritus
Greek Philosopher
-Atoms constantly move
-Atoms are "uncuttable."
-Atoms are small, hard particles -
440
Democritus Atomic Model
-
John Dalton
-All substances are made up of atoms
-Atoms of different elements are different
-Atoms of the same element are exactly alike
-Elements combine in specific proportions
-He conducting in experiments combining elements -
John Dalton Atomic Model
-
J.J. Thompson
-He conducted the Cathode-tube experiment
- His theory of the atomic structure lead to the "plum-pudding" model
-There are small, negatively charged particles inside an atom -
J.J Thompson
-
Ernest Rutherford
British Chemist and Physicist
-Atoms contain mostly empty space
-Electrons move in empty space in the atom
-He conducted the gold-foil experiement
-Most of an atom's mass is in the nucleus
-There is a small, dense, positively charged nucleus -
Ernest Rutherford Atomic Model
-
Niels Bohr
-Electrons jump between levels from path to path
-Electrons travel in definite paths -
Niels Bohr Atomic Mode;
-
Erwin Schrodinger and Werner Heisenberg
-Electrons paths cannot be predicted
-Electrons are found in electron clouds not paths -
Erwin Schrodinger and Werner Heisenberg Atomic model