Question

main postulates of rutherford atomic model and the cause of failure of this model

Answer 1

Postulates of Rutherford Atomic model are:
1. There is a positively charged centre in the atom called the nucleus. All the mass of an atom reside into the nucleus.
2.The electrons revolve around the nucleus in circular paths.
3.The size of the nucleus is very small as compared to that of the atom.
Failure or Drawbacks:
Although Rutherford model of the atom explained the nucleus in the atom. He could not explain the revolution of electrons in circular paths. An object in a revolution would radiate energy and thus the electrons would lose energy and fall toward the nucleus. Thus the atom should collapse very quickly and the matter should not be in state as we know today.We know that atoms are quite stable.
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Answer 2

Rutherford postulated that

1. Most of the mass and all of the charge of an atom concentrated in a very small region is called atomic nucleus.

2. Nucleus is positively charged and it's size is of the order of 10–15 m ≈1 Fermi.

3. In an atom there is maximum empty space and the electrons revolve around the nucleus in the same way as the planets revolve around the sun.

Drawbacks of Rutherford's Atomic model:

1. Stability of atom: This could not explain stability of atom because according to classical electrodynamics theory an accelerated charged particle should continuously radiate energy. Thus an electron moving in an circular path around the nucleus should also radiate energy and thus move into smaller and smaller orbits of gradually decreasing radius and it should ultimately fall into nucleus.

2. According to this model the spectrum of atom must be continuous where as practically it is a line spectrum.

3. The model did not explain the distribution of electrons outside the nucleus.