Question

Write two limitations of Bohr’s model.

Answer 1

When physicists were struggling hard to understand the hydrogen spectra’s discrete wavelengths, Bohr’s model was a great success. In Bohr’s model, the electrons are considered to be revolving around the nucleus. But there were limitations to this model. Consider the condition applied on the atom in Bohr’s model. Also, the Bohr’s model gives you the position and momentum of the particle simultaneously.

Complete answer:
Bohr came up with his model by making few assumptions which are called postulates. The electron revolves around the nucleus in circular orbits, the radii of these orbits are unique and each orbit corresponds to a unique value of energy of electrons. While deriving this energy, the atoms which were considered, were hydrogen like atoms.

This theory is applicable only for hydrogen like atoms, meaning that the atom must have only one electron. It can be a hydrogen atom or some other ions having only one electron. Hence, one limitation of Bohr’s model is, it cannot be extended for those atoms or ions which have more than one electron.

As it was said earlier, Bohr’s model gives you the position as well as the momentum of the particle simultaneously. But according to Heisenberg's uncertainty principle, position and momentum of a particle possessing dual nature (particle and wave) cannot be determined simultaneously. Hence, Bohr's model violates the Heisenberg's uncertainty principle, this is one more limitation of Bohr’s model.

Note: Remember that the Bohr’s model is based on conditions which deals with position and velocity of the electrons simultaneously. Also remember that the Bohr’s model is only applicable for atoms which have only one electron, meaning that the atom can only be a hydrogen atom or some other ion. Not applicable for atoms having more than one electron.