Experiments performed by J.J.Thomson to discover electron.

1. JJ THOMSON EXPERIMENT (1897)

2. CATHODE RAY TUBE

3. EXPERIMENT 1

4. CATHODE RAY TUBE

5. A Cathode Ray Tube
Source of
Electrical
Potential
Metal Plate
Stream of negative
particles (electrons)
Gas-filled
glass tube Metal plate
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 58

6. Thomson’s Experiment
- cathode Anode +

7. Thomson’s Experiment
- cathode anode +

8. Thomson’s Experiment
- +
• Passing an electric current makes a
beam appear to move from the
negative to the positive end.

9. Thomson’s Experiment
- +
• Passing an electric current makes
a beam appear to move from the
negative to the positive end.

11. INFERENCE????

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

13. Experiment 2

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

19. EXPERIMENT 3

20. ON APPLICATION OF
ELECTRICAL FIELD

21. Thompson’s Experiment
• By adding an electric field

22. Thompson’s Experiment
• By adding an electric field

23. Thompson’s Experiment
• By adding an electric field he
found the moving particles
were negative

24. INFERENCE
•THE GLOW IS
PRODUCED BY
NEGATIVELY
CHARGED
PARTICLES.

25. EXPERIMENT 4

26. CHANGED CONDITIONS
BUT
SAME RESULT OBTAINED

27. INFERENCE?
•THERE ARE
NEGATIVELY
CHARGED
PARTICLES IN ALL
SUBSTANCES.

28. THUS, ELECTRON
WAS DISCOVERED

29. JJ THOMSON MODEL OF ATOM-PLUM
PUDDING MODEL

30. THANKYOU