Explain the limitations of the Bohr atomic model.

(N/A) $(1)$ The Bohr model is applicable only to hydrogenic atoms. It cannot be extended even to simple two-electron atoms such as helium.
- The analysis of atoms with more than one electron was attempted using the lines of Bohr's model for hydrogenic atoms,but it did not meet with any success.
- The difficulty lies in the fact that each electron interacts not only with the positively charged nucleus but also with all other electrons.
- The formulation of the Bohr model involves the electrical force between the positively charged nucleus and the electron. It does not include the electrical force between electrons,which necessarily appears in multi-electron atoms.
$(2)$ While the Bohr model correctly predicts the frequencies of the light emitted by hydrogenic atoms,it is unable to explain the relative intensities of the frequencies in the spectrum.
- In the emission spectrum of hydrogen,some of the visible frequencies have weak intensity,while others are strong. Why?
- Experimental observations depict that some transitions are more favoured than others.
- The Bohr model is unable to account for these intensity variations.
- This model cannot be applied to complex atoms. For complex atoms,we must use a new theory based on quantum mechanics.