-
400
Democritus
Proposed that matter is made of small unbreakable particles call atoms.
Atoms are solid. -
400
Aristotle
Stated that all substances are made of 4 elements.
1. Fire
2. Water
3. Air
4. Earth -
John Dalton
Transformed Democritus' ideas on atoms into a modern atomic model.
All matter is made of tiny microscopic particles called atoms. -
J.J. Thomson
Discovered the electron and conducted the cathode ray tube experiment.
By adding an electric charge he found that the moving pieces were (negative) opposites. -
Robert Millikan
Determined the mass and chaarge of the electron. Robert conducted oil drop experiment by measuring the effect of an elctric field on very small oil droplets. -
Ernest Rutherford
Ernest Rutherford discovered the nucleus. The nucleus is made up of mostly +charge and mass. -
Neils Bohr
He proposed that an electron is found only in specific circular paths. -
Sir James Chadwich
Confirmed the existence of the nuetron in the nucleus.