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JJ THOMSON

Irene Suárez Rodríguez

Created on September 9, 2023

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J.J. Thomson

Who was J.J. Thomson?

Thomson's model of the atom

Joseph John Tomson, better know as J.J. Thomson, was a British scientist who discovered the electron . He received the Nobel Prize in physics in 1.906 for his work on the electron.

J.J. Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negative charged subatomic particles or electrons. With these discoveries, he proposed his atomic model, later called the plum pudding model of the atom.

To understand Thomson's experiments we must first know how cathode rays are formed. Crookes tube: is a tube without air inside and with two plates inside, each of wich is either positively or negativeli charged, the left-hand plate is negatively charged and is called the cathode, and the right-hand plate, wich is positively charged, is called the anode. Betwen these two electric charged plates there is a light that goes from the cathode to the anode, this light is the cathode ray. Thomson made a few changes in the crookes tube for his experiments:

Experiments

3rd experiment

2nd experiment

1st experiment

For the second experiment he put a positive charge on one side of the container and a negative charge on the other side, the ray always deflected towards the positive, that's how he proved that cathode rays have a negative charge.

The third experiment was the same as the second, but in this one he put more electric charge in the sides of the container and the ray deflected even more. Thus he showed that the deflection of the rays is proportional to the magnitude of the electric field.

In his first experiment he he put a small mill inside the glass container, when the cathode ray passed trouhg the mill it moved. With this experiment he proved that cathode rays have mass.

In general he discovered that canonical rays are composed of negatively charged particles called electrons, the relationship between the mass and charge of these particles, and proposed his atomic model.

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