When connected to an electric source, the tube glowed. The glowing beam, which travels from the cathode to the anode, is called a cathode ray. JJ Thomson found that the cathode rays could be deflected by either magnets or electrically charged plates. He also found the mass of an electron. Nuclear Changes A. Nuclear reactions change the composition of an atom's nucleus.
Unstable nuclei are radioactive.
Protons and neutrons are held together by these nuclear forces. Because neutrons have no elec chg, the nuclear forces bet them are the only forces bet them. 1. see chart p 114 2.