Compare all the proposed models of an atom given in this
chapter.
Answers
Answer:
Thompson Model Rutherford Model Bohr Model
In this model, an atom consists of a positively charged sphere and the electrons embedded in it. The number of electrons is equal to the number of protons so the atom is electrically neutral. In this model, there is a positively charged centre in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus. The electrons revolve around the nucleus in circular paths. The size of the nucleus is very small as compared to the size of the atom.
In this model, only certain special orbits known as the discrete orbit of electrons, are allowed inside the atom. While revolving the electrons do not radiate energy. These orbits are called energy levels or shells.
Answer:
J. Thomson:
An atom as a whole is electrically neutral because the negative and positive charges are equal in magnitude. J. J. Thomson suggested that electrons are embedded in a sphere of positive charge.
E. Rutherford:
The gold foil experiments of Rutherford suggested that all the positive charge is located in a very small space which is 10 times the radius of an atom. Therefore, Rutherford gave a model in which electrons are revolving round the nucleus.
Neils Bohr:
To explain the stability of an atom and atomic spectra, Bohr suggested that electrons are moving round the nucleus in orbits which have fixed energy shells. There is a loss or gain in energy of electron when it moves from one orbit to the other.