Class 12 Physics Board Exam 2026 is scheduled for February 21, 2026. During this time, students must practice Atoms Class 12 Important Questions to secure good marks from Chapter 12.
The Atoms chapter is concept-based yet highly scoring because most questions are formula-based, diagram-oriented, and derivation-focused. Board papers frequently include numericals from Bohr’s model, energy level calculations, and spectral series. Practicing Atoms Class 12 Question Answers along with properly structured explanations can significantly improve accuracy and confidence.
Students should also revise Atoms Class 12 MCQ, as competency-based and assertion-reason questions are now common in board exams.
Atoms Class 12 Important Questions
Preparing Atoms Class 12 Important Questions ensures clarity in the core topics of atomic structure and spectral analysis. The chapter primarily revolves around Rutherford’s atomic model, its limitations, Bohr’s model of hydrogen atom, Energy levels and quantization, and more.
Solving structured Atoms Class 12 Question Answers regularly ensures conceptual clarity and strong formula application.
Thus, it is independent of n. Thus (A) is correct option.
(D)
Sol. Total energy of hydrogen atom in ground state,
E = –13.6 eV
Potential energy of the electron in ground state,
P = 2 × E
= 2 × (–13.6) = –27.2 eV
Thus (D) is correct option.
3. The total energy of an electron in the first excited state of hydrogen atom is about –3.4eV. Its kinetic energy in this state is [SQP 2010]
(A) –3.4 eV
(B) 3.4 eV
(C) –6.8 eV
(D) 6.8 eV
(B)
Sol. Total energy of electron in first excited state,
E = –3.4 eV
Kinetic energy of electron in first excited state,
EK = – E = – (–3.4) = 3.4 eV
Thus (B) is correct option.
4. What is the ratio of radii of the orbits corresponding to first excited state and ground state, in a hydrogen atom? [OD 2021]
5. In the Rutherford scattering experiment, the distance of closest approach for an –particles is d0. If –particles is replaced by a proton, then how much kinetic energy in comparison to –particle will be required to have the same distance of closest approach d0? [Delhi 2017]
6. Define ionization energy. How would the ionization energy change when electron in hydrogen atom is replaced by a particle of mass 200 times that of the electron but having the same charge? [Delhi 2019]
7. A proton of energy 1.6 MeV approaches a gold nucleus (Z = 79). Find the distance of its closest approach. [OD 2024]
8. A hydrogen atom initially in its ground absorbs a photon and is in the excited state with energy 12.5 eV. Calculate the longest wavelength of the radiation emitted and identify the series to which it belongs.
9. Using Bohr's second postulate of quantisation of orbital angular momentum show that the circumference of the electron in the nth orbital state in hydrogen atom is n–times the de–Broglie wavelength associated with it. [OD 2016, Comp 2008]
Sol. Bohr's second postulate states that the electron revolves around the nucleus in certain privileged orbit which satisfy certain quantum condition that angular momentum of an electron is an integral
10. Calculate the shortest wavelength of the spectral lines emitted in balmer series.
Important Derivations and Numericals to Prepare
To score well in the exam, students must thoroughly revise the following:
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Bohr’s Postulates: Understand quantization of angular momentum and stationary orbits.
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Radius of nth Orbit: Derivation and formula-based numericals are frequently asked.
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Energy of Electron in Hydrogen Atom: Important for 3–5 mark derivation questions.
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Spectral Series: Lyman, Balmer, and Paschen series-based wavelength calculations.
These topics are commonly tested, and revising detailed Atoms 12 Solutions helps students understand how each step carries marks.