Merits and Limitations of Bohr’s theory
Merits of Bohr’s Theory:
1. The experimental value of radii and energies in hydrogen atom are in good agreement with that calculated on the basis of Bohr’s theory.
2. Bohr’s concept of stationary state of electron explains the emission and absorption spectra of hydrogen like atoms.
3. The experimental values of the spectral lines of the hydrogen spectrum are in close
agreement with that calculated by Bohr’s theory.
Limitations of Bohr’s Theory:
1. It does not explain the spectra of atoms having more than one electron.
2. Bohr’s atomic model failed to account for the effect of 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.
3. De Broglie suggested that electrons like light have dual character. It has particle and wave character. Bohr treated the electron only as particle.
4. 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.