JEE Physics 2025 Question with Solution

Given:

• 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.

Find: The correct option.

The Bohr model describes hydrogen and hydrogen-like species such as $\mathrm{He^+}$, $\mathrm{Li^{2+}}$ and similar one-electron systems. It works for these atoms because only the nucleus-electron attraction needs to be considered.

In multi-electron atoms, electron-electron repulsive interaction becomes important. The Bohr model does not include this repulsive force between electrons, so it cannot correctly explain such atoms.

Therefore, Assertion A is true and Reason R is also true. Further, R correctly explains A.

The correct option is C.

Given:

• The question asks whether Assertion A and Reason R are true, and whether R explains A.

Find: The correct relationship between Assertion A and Reason R.

Assertion A: The Bohr model is applicable only to hydrogen and hydrogen-like atoms.

This statement is true because the Bohr model successfully explains the spectra of one-electron systems only.

Hydrogen-like atoms are single-electron species such as $\mathrm{He^+}$, $\mathrm{Li^{2+}}$ and $\mathrm{Be^{3+}}$. For atoms containing more than one electron, the model fails to predict the correct spectra.

Reason R: The formulation of the Bohr model does not include the repulsive force between electrons.

This statement is also true. The model is built for an electron moving around the nucleus in quantized orbits and does not account for inter-electronic repulsion.

Since multi-electron atoms involve significant electron-electron interactions, neglecting this effect makes the Bohr model unsuitable for them. Hence, the reason directly explains the assertion.

Therefore, both A and R are true, and R is the correct explanation of A. The correct option is C.