Question

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : The Bohr model is applicable to hydrogen and hydrogen-like atoms only. Reason R : The formulation of Bohr model does not include repulsive force between electrons. In the light of the above statements, choose the correct answer from the options given below :

• A. Both A and R are true but R is NOT the correct explanation of A.
• B. A is false but R is true.
• C. Both A and R are true and R is the correct explanation of A.
• D. A is true but R is false.

Hint:

The Bohr model is a foundational model in atomic physics but has limitations. Remember that it works well for single-electron systems because it neglects the complexities of electron-electron interactions. For multi-electron atoms, more sophisticated models like the quantum mechanical model are necessary.

Answer 1

The Correct Option is C

Assertion A states that the Bohr model is applicable to hydrogen and hydrogen-like atoms only. 
Hydrogen-like atoms are those that have only one electron, such as \( He^+, Li^{2+}, Be^{3+} \), etc. 
The Bohr model successfully explains the atomic spectra of hydrogen and these single-electron species. 
For atoms with more than one electron, the Bohr model fails to predict the correct spectra. 
Thus, Assertion A is true. Reason R states that the formulation of the Bohr model does not include the repulsive force between electrons. 
The Bohr model is a simplified model of the atom that considers electrons orbiting the nucleus in specific quantized energy levels. 
It does not take into account the inter-electronic repulsions that are significant in multi-electron atoms. 
The absence of consideration for electron-electron repulsion is a primary reason why the Bohr model is only accurate for single-electron systems. Thus, Reason R is also true. Furthermore, the reason R correctly explains why the Bohr model is limited to hydrogen and hydrogen-like atoms. The simplicity of having only one electron eliminates the complexities arising from electron-electron interactions, which are not accounted for in the Bohr model. Therefore, Reason R is the correct explanation of Assertion A.