Question

write the demerit of ruther ford and bhor model?​

Answer 1

Answer:

Limitations of Bohr’s theory:

(i) It does not explain the spectra of atoms having more than one electron.

(ii) Bohr’s atomic model failed to account for the effect of the magnetic field (Zeeman Effect) or electric field (Stark effect) on the spectra of atoms or ions. It was observed that when the source of a spectrum is placed in a strong magnetic or electric field, each spectral line further splits into a number of lines. This observation could not be explained on the basis of Bohr’s model.

(iii) De Broglie suggested that electrons like light have a dual character. It has particle and wave character. Bohr treated the electron only as a particle.

(iv) Another objection to Bohr’s theory came from Heisenberg’s Uncertainty Principle. According to this principle “It is impossible to determine simultaneously the exact position and momentum of a small moving particle like an electron”. The postulate of Bohr, that electrons revolve in well-defined orbits around the nucleus with well-defined velocities is thus not tenable.

Drawbacks of Rutherford’s model of atom

Rutherford proposed that electrons revolve at a high speed in circular orbits around the positively charged nucleus. When a charged particle i. e. electron revolves around positively charge nucleus, it needs to be accelerated so as to keep it moving in circular orbits. However, according to electromagnetic theory, whenever a charged particle such as an electron is accelerated around another charged center ( nucleus ) which are under force of attraction, there will be continuous radiation of energy. This loss of energy would slow down the speed of the electron. This would reduce the radius of the electron–orbit. Eventually the electron would fall into the nucleus. The result would be that the atom would collapse. But this does not happen. Thus Rutherford’s atom could not explain the stability of the atom. Failure of Rutherford’s model i.e. reduction of radius of orbit is shown below.

Rutherford proposed that electrons revolve around the nucleus in the fixed orbits. However, he did not specify the orbits and the number of electrons in each orbit.