-
400
Aristotle
Did not believe in original atomic theory.
Believed all mater was made up of four elements.
Poeple believed him. -
460
Democritus
Thought everything cold be broken too smaller pieces.
Formulated atomic theory for universe.
To him the atom looked like a marble. -
Dalton
Developed Atomic Theory.
Believed atom was smallest unit of matter.
Also believed atom looked like marble. -
Crookes
Developed vacuum pump that allowed him to produce cathode-ray tubes with a smaller residual gas pressure -
Joseph Thomson
Discovered electron using cathode-ray tube.
Plum Pudding Model.
Mass Spectograph. -
The Curies
Discovered polonium and radium. Were married. -
Milikan
Oil drop experiment.
Discovered how to find an atoms charge.
Proved sumatomic particles exist. -
Rutherford
Discovered nucleus.
Theory was atom has a positive nucleus with negative electrons around it. Planetary system model. Student of J.J. Thomson. -
Moseley
Xray tubes determined charges on nuclei. Found relationship between wavelengths -
Bohr
Developed Bohr Model. Said electrons were on special orbit.