Atomic Structure

DISCOVERY OF PROTON (POSITIVE RAYS OR CANAL RAYS)

Matter is neutral. With the discovery of electron in the atom of the matter, one can conclude that there must be a positively charged particles which will balance the effect of the negatively charged electrons. The first evidence of positive particles came from the studies of Eugene Goldstein 1886.
Goldstien experiments was carried out in a modified gas discharge tube, shown in figure:-

Goldstein used the above cathode ray tube. In this tube cathode was perforated containing canals some fluorescent material was placed behind to cathode he observed that this cathode ray tube not only contain cathode rays but there are also rays traveling in a direction opposite to that of the cathode rays. When high voltage was applied, cathode rays started traveling from cathode toward the anode. Cathode rays possesses kinetic energy therefore when they will collide with the atoms/ molecules of the gas present in the tube, they will remove one electron from each atom or molecule. When hydrogen gas was used in the tube and the electron present in it was removed by the cathode rays only radius (positively charged) will be left. The positively charge nucleus which may be called as proton was attracted toward the perforated cathode. They passed through the perforation (canals) of the cathode producing florescence on the screen. As these rays passed through the canal, therefore they are also called as canal rays.