Shortcomings of Bohr's theory
Bohr's theory was able to explain successfully a number of experimental observations and has correctly predicted the spectral lines of hydrogen atom. However, the theory fails in the following aspects.
1) The theory could not account for the spectra of atoms more complex than hydrogen.
2) The theory does not give any information regarding the distribution and arrangement of electrons in an atom.
3) It does not explain, the experimentally observed variations in intensity of the spectral lines of the element.
4) When the spectral line of hydrogen atom is examined by spectrometers having high resolving power, it is found that a single line is composed of two or more close components. This is known as the fine structure of spectral lines. Bohr's theory could not account for the fine structure of spectral lines.
It is found that when electric or magnetic field is applied to the atom, each of the spectral line split into several lines. The former effect is called as Stark effect, while the latter is known as Zeeman effect. Bohr's theory could not explain the Stark effect and Zeeman effect.