Introduction to Structure of an Atom

Atoms

Atoms are the building blocks of matter. It is the smallest unit of matter that is composed of three sub-atomic particles: the proton, the neutron and the electron.

Cathode ray experiment

• J. J. Thomson discovered the existence of electrons.
• He did this using a cathode ray tube, which is a vacuum-sealed tube with a cathode and anode on one end that created a beam of electrons travelling towards the other end of the tube.
• The air inside the chamber is subjected to high voltage and electricity flows through the air from the negative electrode to the positive electrode.
• The characteristics of cathode rays (electrons) do not depend upon the material of electrodes and the nature of the gas present in the cathode ray tube.
• The experiment showed that the atom was not a simple, indivisible particle and contained at least one subatomic particle – the electron.