Eugen Goldstein in 1886, using a modified cathode ray tube containing hydrogen and a cathode perforated inside, observed that apart from the cathode rays (electrons), there was a luminescence that moved away from the anode (positive pole) and towards the cathode. He called this type of rays channel rays. Goldstein assumed that this type of rays was due to the presence of positive particles, which in 1906, Thomson managed to determine that they had a charge equal to that of the electron, but with opposite sign (+1.6 x 10-19 C), which Rutherford later named the proton.
Goldstein’s conclusion
- Electric and magnetic fields deflect particles in a way that is consistent with the deflections that positively charged particles might experience.
- The charge-to-mass ratio for these rays is much lower than that for electrons.
- The charge-to-mass ratio depends on the gas contained in the tube. For hydrogen gas the ratio is the highest, but for other gases it is a whole fraction of the ratio for hydrogen gas.
A conclusion consistent with the observational record is that all atoms have units of positive charge and that atoms have integer multiples of these units established for the hydrogen atom.
In 1932, James Chadwick detected the existence of a particle in the interior of the nucleus, without charge, with a high penetrating power and with a mass similar to that of the proton that avoided the repulsion between them, which he called neutron.
In spite of the complexity of the atom we can consider it formed mainly of electrons, protons and neutrons.
