Cathode Ray
They are streams of electrons observed in vacuum tubes. However! scientist at the time did not know they were electrons. At the time, it was assumed that the atom was the smallest particle.
Cathode ray tube
The cathode is a negatively-charged conductor, and the anode is a positively-charged conductor.
Electrons, which have a negative charge, flow off the cathode and are attracted towards the anode.
A small hole in the anode allows some electrons to pass through it, creating a beam of electrons.
Rutherford knew that Alpha particles had had mass and velocity. He hypothisized that these particles would go through the gold foil, and may scatter a bit because of the original belief of "the blueberry muffin".
After shooting alpha particles through the thin sheet of gold, Geiger, Marsden and Rutherford discovered that a small amount of molecules were scattered at larger than 90° angles.
The original thought of "the blueberry muffin" cannot explain why these particles scattered larger than 90.
This caused them to conclude that there was a small fraction of the total volume of the atom that held most of the mass of the atom.
J.J Thomson's 3 experiments
Before Thomson's experiments, it had already been discovered that the cathode rays deposit an electric charge. This was done by putting an electrometer at the opposite end from the cathode and anode. When the cathode rays hit the electrometer, it measured an electric charge.
The first experiment was done in order to see if the charge was separate from the cathode rays. Thomson used a magnet to bend the cathode rays away from the electrometers. When he did this, he discovered that the electrometers stopped measuring electric charge.
Next, J.J. Thomson set out to determine if the charge carried by the cathode rays was negative or positive. To do this he would use an electric field. He put a negatively charged metal plate on one side of the cathode rays let out past the anode, and a positively charged metal plate on the other side. When the charged metal plates were introduced he found that the cathode rays bent toward the positive plate and away from the negative plate. This showed that the charge carried by the cathode rays was negative.
