CBSE Class 9 Answered

Drawbacks of model of atom proposed by Rutherford are as follows:

1. An electron which is revolving around the nucleus gets accelerated towards the nucleus. According to the electromagnetic theory, an accelerating charged particle must emit radiation, and lose energy. Because of this loss of energy, the electron would slow down, and will not be able to withstand the attraction of the nucleus. As a result, the electron should follow a spiral path, and ultimately fall into nucleus. If it happens then the atom should collapse in about 10-8 second. But, this does not happen: atoms are stable. This indicates that there is something wrong in the Rutherford’ mass nuclear model of atom.

2. The Rutherford’s model of atom does not say anything about the arrangement of electrons in an atom.

Drawbacks of model of atom proposed by Thomson are as follows:

J.J. Thomson proposed that atom consists of a positively charged sphere with embedded electrons in it. But, later it was found that the atom has concentrated mass and the positively charged nucleus is at the centre while the negatively charged electrons move in the shells around the nucleus.