J.J. Thomson's atomic model

Joseph John Thomson was Danish Physicist, who discovered the 'electrons' in 1897 and put forward his famous ‘plum pudding model’ of atom in 1904.The structure of atom was put forth by many scientists. John Dalton, J.J. Thomson, Rutherford and Bohr are the important scientists who worked in this field.

The following are the work of various scientists in framing the structure of atom:

• John Dalton discovered that matter is made of very small particles called atoms which can not be divided.
• J.J. Thomson discovered electrons and found that the atom can be divided and it is made of positive core and negatively charged particles embedded in it.
• James Chadwick discovered the protons.
• Goldstein discovered neutrons.
• Rutherford discovered that atom has a positive central core called nucleus and the electrons move around the nucleus in great speed.
• Bohr stated that the electrons move around the nucleus in a definite energy levels called shells and gave the explanation for the stability of atom.

Discovery of Atom

It was John Dalton, who stated that the matter is made of indivisible small particles called atoms. Atom means 'that which can not be divided'. This model was discarded by J.J. Thomson when he discovered the electrons.

J.j. Thosmson Atomic Model

 Michael Faraday worked on the passage of electricity through liquids while Thomson worked on the passage of electricity through gases. During this experiment, Thomson discovered the electrons.
According to Thomson, when a glass tube fitted with two electrodes filled with a gas at low pressure and when a high voltage of electricity is applied, some rays are generated from the cathode. He named these rays as cathode rays. When two charged plates are placed on either side of this discharge tube, these rays (cathode rays) are attracted to the positive plate. Hence he said that the cathode rays are made of negatively charged particles. He called these particles as ‘corpuscles’. Corpuscles mean particles. G. J. Stoney named them as ‘electrons’

In J.J. Thomson atomic model, the atom consists of a sphere of uniform distribution of positive charge with electrons embedded in it. The number of positive particles is equal to the number of electrons and the 'atom as a whole is eclectically neutral'. This model accounted for the neutrality of atom. This model is popularly known as"plum pudding model", like negatively-charged "plums" surrounded by positively-charged "pudding".

But later Rutherford proved that the electrons are not embedded in the positive sphere, but they revolve around the positive central core and he named it as nucleus