Natasha Isaacs
Embedded Files
1897
Thomson
Joseph John Thomas
Joseph John Thomson was the person that had discovered electrons in an atom. However before that, he was born in Cheetham Hill, Manchester, England on December 18th of 1856. (Sagittarius). At just fourteen years old, he had enrolled in Owens college (now known as Victoria University). Thomson's father wanted him to study engineering, however they couldn't financially afford it. In 1884 he had won an Adams Prize for his book, 'Treatise on the Motion of Vortex Rings'.
Atom discovery
What was Thomson's Experiment? (It's a lot)
Thomson's discovery begins with an experiment involving Cathode ray tubes ( the picture on the left). These were sealed, compacted tubes and high voltage charge. At the end of both ends were metal plates that were oppositely charged, causing The cathode ray was deflected away from the negative charged electric plate (Cathode) and towards the positive charged plate (Anode). After similar experiments, including JJ placing 2 magnets on both sides and noted that the magnetic field also deflected the cathode ray, giving JJ the conclusion that 1, the cathode ray was made up of negatively charged particles.the mass of each particle was much smaller than that of any atom that we know of.
This video goes into detail on how the electron was discovered. She speaks about how Thomson used an oppositely charged plates with the high voltage battery and a pressure reducing vacuum to see the results. The video then shows an animated version of this experiment, that caused a green-yellow mix of light to appear before Thomson's own eyes which are cathode rays that traveled from the negative charged plate to the positive charged plate. He then conducts other experiments to take note on other discoveries, Another experiment he used an electric field, making the rays change paths upon the change. This showed Thomson that the rays are made up of negatively charged particles known as Electrons
What was his Atomic Model?
Thomson then creates the "plum pudding model" which depicts of negative charged particles embedded in a sea of positive charge mass. Thomson had known that an atom was a neutral charge. Thomson had thought there must be a kind of positive charge inside the atom to balance the negative charge on the electrons in order to make it neutral. The little spots represent the negative particles while the "pudding part" represents the postive mass.
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