JJ Thomson used experiments to describe how atoms behaved in experiments done by Faraday (electroplating), observations made by Crooke (cathode ray tube) and observations made by Bequerel (radioactivity).
Thomson is credited with discovering the electron based on his explanation of how the cathode ray behaved when they were introduced to a magnet.
A cathode is made of a piece of metal, SO the Ray created by the cathode MUST be coming out of an atom of the metal ... if the magnet was held in one direction, the ray would push away from the north pole but when flipped, it would move towards the north pole.
Dalton's model did not take into account positive and negative charges. Through these experiments with cathode ray tubes he said there MUST be both positive and negative charges in an atom.
Can you explain what is meant by charge to mass ratio? If you can, explain this to Mr. Nannan!
JJ Thomson's model placed both positive and negative charges in an atom ... SO an atom is NOT the smallest particle in matter, Like Dalton thought.
Millikan furthered this to determine the actual charge of one of these negative things (electron) which is the same as the positive thing (proton)
Rutherford made other observations that changed this model slightly ...