-
400 BCE
Democritus
Discovered:
- Atoms are "uncuttable."
-Atoms are small, hard particles.
- Atoms constantly move. -
400 BCE
Democritus
Created the Atomic Model -
Period: 400 BCE to
Atomic Theory Timeline
-
John Dalton
-Conducted experiments in combining elements Discovered:
-All substances are made of atoms
-Atoms of different elements are different
-Atoms of the same element are exactly alike.
-Elements combine in specific proportions -
John Dalton
Created the Billiard Ball Model -
J.J. Thomson
-Discovered that there are small, negatively charged particles inside an atom. -He conducted the cathode-ray tube experiment -
J.J. Thomson
His theory of the atomic structure lead to the "plum-pudding" model. -
Rutherford
Discovered:
-Atoms contain mostly empty space
-Electrons move in empty space in the atom
-Most of an atom's mass is in the nucleus
-There's a small, dense, positively charged nucleus -He conducted the gold foil experiment -
Ernest Rutherford
Created the Model Of An Atom -
Neils Bohr
Discovered:
-Electrons jump between levels from path to path.
-Electrons travel in definite paths -
Neils Bohr
Created the Bohr Model -
Erwin Schrodinger and Werner Heisenberg
Discovered:
-Electron paths cannot be predicted.
-Electrons are found in electron clouds, not paths. -
Erwin Schrodinger and Werner Heisenberg
Created the Quantum Mechanical Model
