Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. In the light of the above statements, choose the correct answer from the options given below
- A is true but R is false
- Both A and R are true and R is the correct explanation of A
- A is false but R is true
- Both A and R are true but R is NOT the correct explanation of A
Answer
(2) Both A and R are true and R is the correct explanation of A
Solution
As per NCERT, the Bohr model is applicable to hydrogenic (one-electron) atoms only, such as H, He+, Li2+; it cannot be extended even to the two-electron helium atom.
In the Bohr model only the electrostatic attraction between the nucleus and one electron is considered.
In a many-electron atom the electrons also repel one another; this repulsion is not included in Bohr's formulation, so the model fails for such atoms.
A is true, R is true, and R explains why the model is limited to hydrogen-like atoms.
Answer: (2)