Question

What are the postulates of Rutherford? What are its drawbacks?

Answer 1

Hint: Postulates of atomic model given by Rutherford include the composition of positively charged particles in the dense nucleus of an atom, the presence of negatively charged electrons which make an atom electrically neutral. The main drawback was the high speed revolving electrons which will lose their energy continuously and will fall into the nucleus finally leading to its collapse. His model represented the instability of an atom which was a disastrous drawback.

Complete Step By Step Solution:
Ernest Rutherford in 1911 presented a model to explain the structure of an atom. Rutherford pictured an atom as being composed of tiny nuclei in which its positive charges and the entire mass seems to be concentrated. His postulates were based on the result of alpha scattering experiments in which streams of alpha particles from a radioactive source were directed at a gold sheet of 100nm thickness. The atom consists of large empty space due to which most alpha particles are left undeviated. The alpha particles felt deflected when they passed near the dense nucleus which signifies that nucleus is quite tiny and the atom consists of a large free space. He proposed that negatively charged electrons surround the nucleus and they revolve at high speed around it in circular paths. The positively charged nucleus and negatively charged electrons are held together by strong electrostatic forces of attraction.
Drawbacks of Rutherford’s Model: The major drawback was that the electrons revolving in circular orbits will release electromagnetic radiations as according to Maxwell; accelerated charged particles release EM radiations. The energy of the EM radiations will be carried from the motion of the revolving electrons which will result in the shrinking of their orbits. This process will carry on leading to the shrinking of orbits which will finally result in the falling of electrons into the nucleus leading to collapse of atoms. This model therefore predicted the instability of the atom which was not acceptable at all.
Another drawback was due to the fact there was no knowledge about the arrangement of electrons in the atom.

Note: The correction to Rutherford’s Model was provided by Neils Bohr. He depicted that electrons are moving around the nucleus in stationary orbits in which they do not lose energy. These orbits are positioned at the values where angular momentum is an integral multiple of reduced Planck’s constant. Since electrons are not losing their energy in these orbits so this depicted the stability of an atom.