Given below are two statements: one is labelled as A s s e r t i o n 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

Both A and R are true and R is the correct explanation of A

Both A and R are true but R is NOT the correct explanation of A

Atoms and Nuclei PYQ — JEE Main 2025 · 3 Apr · Shift 2 · Q68 with Solution

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Correct answer: B

Understand the assertion

Assertion A: The Bohr model is applicable to hydrogen and hydrogen-like atoms only.
- Hydrogen has only one electron.
- Hydrogen-like atoms/ions such as $\mathrm{He^+}$ , $\mathrm{Li^{2+}}$ , etc., also have only one electron.
- Bohr model assumes a single electron moving under the Coulomb attraction of the nucleus.
Therefore, Assertion A is true.
Understand the reason

Reason R: The formulation of Bohr model does not include repulsive force between electrons.
- In multi-electron atoms, electrons repel each other.
- Bohr's theory does not account for electron-electron interaction.
- Hence, it fails for atoms having more than one electron.
Therefore, Reason R is also true.
Check whether R explains A
- Bohr model works well only when there is a single electron.
- In hydrogen and hydrogen-like species, there is no electron-electron repulsion.
- In multi-electron atoms, electron-electron repulsion is important, but Bohr model ignores it.
So, Reason R correctly explains Assertion A.
Evaluate options
- A: $\mathbf{A}$ is true but $\mathbf{R}$ is false $\rightarrow$ Incorrect
- B: Both $\mathbf{A}$ and $\mathbf{R}$ are true and $\mathbf{R}$ is the correct explanation of $\mathbf{A}$ $\rightarrow$ Correct
- C: $\mathbf{A}$ is false but $\mathbf{R}$ is true $\rightarrow$ Incorrect
- D: Both $\mathbf{A}$ and $\mathbf{R}$ are true but $\mathbf{R}$ is NOT the correct explanation of $\mathbf{A}$ $\rightarrow$ Incorrect
Final answer

The correct option is B.

View written solutionFree

Correct answer: B

Understand the assertion

Assertion A: The Bohr model is applicable to hydrogen and hydrogen-like atoms only.
- Hydrogen has only one electron.
- Hydrogen-like atoms/ions such as $\mathrm{He^+}$ , $\mathrm{Li^{2+}}$ , etc., also have only one electron.
- Bohr model assumes a single electron moving under the Coulomb attraction of the nucleus.
Therefore, Assertion A is true.
Understand the reason

Reason R: The formulation of Bohr model does not include repulsive force between electrons.
- In multi-electron atoms, electrons repel each other.
- Bohr's theory does not account for electron-electron interaction.
- Hence, it fails for atoms having more than one electron.
Therefore, Reason R is also true.
Check whether R explains A
- Bohr model works well only when there is a single electron.
- In hydrogen and hydrogen-like species, there is no electron-electron repulsion.
- In multi-electron atoms, electron-electron repulsion is important, but Bohr model ignores it.
So, Reason R correctly explains Assertion A.
Evaluate options
- A: $\mathbf{A}$ is true but $\mathbf{R}$ is false $\rightarrow$ Incorrect
- B: Both $\mathbf{A}$ and $\mathbf{R}$ are true and $\mathbf{R}$ is the correct explanation of $\mathbf{A}$ $\rightarrow$ Correct
- C: $\mathbf{A}$ is false but $\mathbf{R}$ is true $\rightarrow$ Incorrect
- D: Both $\mathbf{A}$ and $\mathbf{R}$ are true but $\mathbf{R}$ is NOT the correct explanation of $\mathbf{A}$ $\rightarrow$ Incorrect
Final answer

The correct option is B.