Compare all the proposed models of atom given in the chapter 3 of the text.

Explanation

Thomson.s model of the atom. Thomson proposed that :
(i) An atom consists of a positively charged sphere and the electrons are embedded in it.
(ii) The negative and positive charges are equal in magnitude. So, the atom as a whole is electrically neutral.
Although Thomson.s model explained that atoms are electrically neutral, the results of experiments carried out by other scientists could not be explained by this model.
Rutherford.s model of an atom. On the basis of his experiment, Rutherford put forward the nuclear model of an atom, which had the following features :
(i) There is a positively charged centre in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus.
(ii) The electrons revolve around the nucleus in well-defined orbits.
(iii) The size of the nucleus is very small as compared to the size of the atom.
Bohr.s model of an atom. In order to overcome the objections raised against Rutherford.s model of the atom. Neils Bohr put forward the following postulates about the model of an atom :
(i) Only certain special orbits known as discrete orbits of electrons, are allowed inside the atom.
(ii) While revolving in discrete orbits the electrons do not radiate energy.