SCH3U History of Atoms

Democritus (400BCE)

first thought of the concept of an atom

sphere

Democritus’ model of atom

Aristole and Plato

suggested four elements: earth, fire, air, and water

John Dalton (1804)

proved the existance of atoms; compounds are the result of atoms joining

atom decides likability of element

Dalton’s founding

J. J. Thomson (1897)

suggested the existance of subatomic particles

Plum Pudding Model

Thomson’s model

Cathode Ray

Thomson’s experiment; passage of electric current through gas

Rutherford (1908)

found large empty space between subatomic particles

Gold Foil Experiment

Rutherford’s experiment; shooting positive atoms → majority passed, few deflected

Beta Particles

positive atoms that Rutherford used in his experiments

Bohr (1913)

suggested existance of electron energy levels

James Chadwick (1920s)

discovered the existance of neutron