Question

J.J Thompson proposed that atoms were made up of positively charged particles with electrons scattered into them. How did he reach this conclusion?

Answer 1

First, J.J Thompson experimented with cathode ray tubes: sealed glass tubes at vaccum (without air inside), with two electrons (cathode and anode). When a high voltage was applied a beam of particles left from the cathode and passed throuhg two charged plates (one negative and one positive).

The beam of particles was deflected toward the positively-charged electric plate, which indeicatedd that the particles were negatively charged.

Given that Thompson experimented with different materials (cathode electrodes), that the results were always the same, and that the mass of the electrons were a small fraction (approximately 1/2000) of the hydrogen atom, he concluded that the negatively particle was part of the atom (a subatomic particle).

Also, given that the atom is neutral, he concluded that there were negative and positive particles in any atom, and he speculated that the negative particles (electrons) were scattered into the positive particles which were way more massive.