Chemisty Unit 1 - Topic 2

Democritus

Democritus

• first to suggest that atoms existed (“atomos”)

• could not explain chemical behavior

• Grandfather of Chemistry

John Dalton

• mass ratio experiments

• Billiard Ball model

• Dalton’s Atomic Theory

J. J. Thomson

• cathode ray experiment

• Plum Pudding model

• discovered the electron

Robert Millikan

• oil drop experiment

• determined the charge and mass of the electron

Ernest Rutherford

• gold foil experiment

• Nuclear model

• discovered the nucleus

James Chadwick

• discovered the neutron

Niels Bohr

• atomic emission/absorption experiments

• Planetary model

• found that electrons move in a fixed path around the nucleus