Advanced Chemistry. Chapter 2. Cathode Ray. Why Do This Experiment?. Thompson was wanting to know the different parts of an atom He was wondering why batteries worked the way they did. The Experiment. J.J Thompson built a cathode ray with one end positive (anode) and one negative (cathode).
Rutherford discovered the atom was hard in the middle because it deflected off the zinc backdrop. He came to discover the nucleus in the middle of the atom