JJ THOMSON EXPERIMENT (1897)

CATHODE RAY TUBE

EXPERIMENT 1

CATHODE RAY TUBE

Source ofElectricalPotential

Metal Plate

Gas-filledglass tube Metal plate

Stream of negativeparticles (electrons)

A Cathode Ray Tube

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 58

Thomson’s Experiment

Anode +- cathode

Thomson’s Experiment

- cathode anode +

Thomson’s Experiment

• Passing an electric current makes a beam appear to move from the negative to the positive end.

- +

Thomson’s Experiment

• Passing an electric current makes a beam appear to move from the negative to the positive end.

- +

INFERENCE????

•A stream of particles could be seen to flow from cathode to anode.

Experiment 2

INFERENCE?• THE CAUSE OF THE GLOW IS THE INVISIBLE RAYS EMITTED FROM THE NEGATIVE METAL PLATE OF THE DISCHARGE TUBE.

EXPERIMENT 3

ON APPLICATION OF ELECTRICAL FIELD

Thompson’s Experiment

•By adding an electric field

Thompson’s Experiment

• By adding an electric field

Thompson’s Experiment

•By adding an electric field he found the moving particles were negative

INFERENCE•THE GLOW IS PRODUCED BY NEGATIVELY CHARGED PARTICLES.

EXPERIMENT 4

CHANGED CONDITIONS

BUT SAME RESULT

OBTAINED

INFERENCE?

•THERE ARE NEGATIVELY CHARGED PARTICLES IN ALL SUBSTANCES.

THUS, ELECTRON

WAS DISCOVERED

JJ THOMSON MODEL OF ATOM-PLUM PUDDING MODEL

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