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.