CHEMISTRY STUDY MATERIAL

 CBSE Class 9 Science Notes Chapter 4 Structure of the Atom Facts that Matter Fundamental particles of an atom: Three particles; electron, proton and neutron from which an atom is consisted of, are called fundamental particles of an atom or sub atomic particles. Discovery of Electron: By J. J. Thomson in 1897. He carried a cathode ray experiment in which observed a stream of negatively charged particles coming out of cathode towards the anode. These particles were named as electrons. Discovery of Proton:  By Ernest Goldstein in 1886. He observed in the same gas discharge tube, with different situations that the anode emitted positive particles which he named as Canal Rays. His experiment led to the discovery of proton. Discovery of Neutron: By J. Chadwick in1932. Neutron is present in the nucleus of all atoms. 1. Thomson’s Model of Atom (by Joseph James Thomson in 1897) Thomson’s model of an atom proposed that: An atom is a uniform sphere of positive charges (due to presence o...