Question

How did J.J Thomson contribute to the atomic theory?

Answer 1

Hint: Some of the assumptions given by Dalton were wrong which he failed to explain about the atom which was further explained by J.J Thomson in his model. He explained that the atom can be subdivided into three particles electrons, protons and neutrons.

Complete step by step answer:
After Dalton’s atomic theory, J.J Thomson modified the atomic theory. He said that atoms are uniformly packed spheres containing positive charged matter filled with negative charged electrons. J.J. Thomson discovered the electrons in 1897. The electrons are recognized as the presence of protons
Thomson assumed that the mass of the electrons is two thousand times lighter than the proton and he said that the atom is composed of thousands of electrons. In the atomic structure of the atom, an atom is surrounded by a cloud containing positive charge protons and negative charge electrons.
Along with Rutherford, J.J. Thomson demonstrated the ionization of air using X-ray. Both of them were the first one to demonstrate it. The Thomson atomic model is similar to the plum pudding model.
The postulates of Thomson atomic model are:
(1) An atom contains a positively charged sphere where electrons are embedded in it.
(2) The atom as a whole is electrically neutral in nature as the negative and positive charges have equal magnitude.
The Thomson atomic model was compared to the watermelon where the watermelon seeds are considered as negatively charged particles and the red part of the watermelon are considered as the positively charged.

Note:
J.J Thomson fails to explain the stability of the atom as he failed to explain how a positive charge proton is able to hold the negatively charged electrons in the atom. It also fails to explain the position of the nucleus in the atom.