Final answer:
J.J. Thomson calculated the charge-to-mass ratio of the electron and found it to be a constant value. This evidence from his experiments aligns with the calculation that the mass of the electron is significantly lower than the mass of any atom.
Step-by-step explanation:
J.J. Thomson conducted experiments with cathode rays and was able to calculate the charge-to-mass ratio of the electron. He found that this value was constant and did not depend on the gas used or the metal electrodes. From this, he concluded that electrons were present in all elements and had a significantly lower mass compared to atoms.