Get the Atoms NCERT PDF for Class 12 Physics directly on this page. Chapter 12 covers the Bohr model, atomic spectra, and Rutherford scattering - all high-yield topics for CBSE, JEE and NEET. The PDF is the official 2026-27 NCERT Part II chapter, free to download below.
- CBSE Weightage: 3 to 4 marks in board papers
- JEE Main Weightage: 1 question per paper (2 to 3%)
- NEET Weightage: 2 to 3 questions per year
Atoms NCERT Section Breakdown - Class 12 Physics Chapter 12
The chapter covers six sections across roughly 22 pages. Sections 12.2, 12.4 and 12.5 carry over 80% of the exam yield for CBSE, JEE and NEET.
| Section | Heading | Page range | Core idea |
|---|---|---|---|
| 12.1 | Introduction | 1 to 2 | Historical models from Thomson to Rutherford, why a model was needed. |
| 12.2 | Alpha-Particle Scattering and Rutherford's Nuclear Model | 3 to 6 | Geiger-Marsden experiment, impact parameter, distance of closest approach, nuclear size estimate. |
| 12.3 | Atomic Spectra | 7 to 8 | Emission and absorption line spectra, characteristic wavelengths. |
| 12.4 | Bohr Model of the Hydrogen Atom | 9 to 14 | Three postulates, orbital radius rn = n2 a0 , energy En = -13.6/n2 eV. |
| 12.5 | The Line Spectra of the Hydrogen Atom | 15 to 18 | Lyman, Balmer, Paschen, Brackett, Pfund series and the Rydberg formula. |
| 12.6 | De Broglie's Explanation of Bohr's Second Postulate | 19 to 22 | Standing-wave derivation of 2π r = nλ , limits of the Bohr model. |
Treat Sections 12.4 and 12.5 as the spine of the chapter. Every NEET and JEE Atoms question from the last five years traces to a formula inside these two sections.
Intext Examples in Class 12 Physics Chapter 12 Atoms
The chapter has about 10 solved Examples. Board papers often rephrase these verbatim as 2 to 3 mark questions.
| Example | Sub-topic | What it Covers |
|---|---|---|
| Example 12.1 | Distance of closest approach in alpha-scattering | Energy conservation, Coulomb potential |
| Example 12.2 | Impact parameter for a given scattering angle | Rutherford formula application |
| Example 12.3 | Bohr radius and electron speed in n=1 orbit | Combined Bohr radius + velocity formulae |
| Example 12.4 | Total energy of hydrogen atom in ground state | En = -13.6/n2 eV |
| Example 12.5 | H-alpha wavelength in Balmer series | Rydberg formula, n=3 to n=2 |
| Example 12.6 | Series limit of Lyman series | Rydberg formula with ni → ∞ |
| Example 12.7 | De Broglie wavelength of orbital electron | λ = h/mv in nth orbit |
| Examples 12.8 to 12.10 | Transition energies, photon frequency, ionisation | Bohr frequency condition, ionisation energy |
The chapter also has 21 numbered Exercises. Exercises 12.5, 12.7 and 12.13 (spectral series) and 12.10, 12.11 (Bohr radius) appear most often in CBSE board and NEET papers. For full worked solutions, see the Atoms Class 12 Physics NCERT Solutions.
Atoms Study Plan for Class 12 Physics Chapter 12
Two focused days are enough to finish the 22-page chapter and work through all exercises.
| Day | Sections | Examples | Exercises | Time |
|---|---|---|---|---|
| Day 1 | 12.1, 12.2, 12.3, 12.4 | Examples 12.1 to 12.4 | Exercises 12.1, 12.2, 12.10, 12.11 | 2.5 hours |
| Day 2 | 12.5, 12.6 | Examples 12.5 to 12.10 | Exercises 12.5, 12.7, 12.13 and revision of all 21 | 2 hours |
Key Formulae for Atoms - Class 12 Physics Chapter 12
Five formulae cover almost every numerical in the Examples, Exercises and past five years of CBSE, JEE and NEET papers.
| Quantity | Formula |
|---|---|
| Energy of nth orbit (hydrogen) | En = -13.6n2 eV |
| Radius of nth orbit | rn = n2 a0 , with a0 = 0.529 Å |
| Bohr angular momentum condition | L = mvr = nh2π |
| Rydberg formula | 1λ = R(1nf2 - 1ni2) , R = 1.097 × 107 m-1 |
| Ionisation energy of hydrogen | 13.6 eV (first excitation energy 10.2 eV) |
For the full master table with all derived quantities, see the Atoms Class 12 Physics Formula Sheet.
Atoms Video Lecture - Class 12 Physics Chapter 12
Source: Next Toppers - 12th Science on YouTube
Previous Year Trends in Atoms - Class 12 Physics
Three question types repeat across CBSE, JEE and NEET every year from this chapter.
- Spectral series identification: NEET 2024 and NEET 2023 both asked which series lies in the visible region. CBSE 2025 framed it as a 2-mark short answer. The Balmer series is the correct answer.
- Bohr radius and energy numerical: JEE Main 2025 asked for r3 / r1 . CBSE 2024 asked for the energy difference between n=2 and n=4.
- Alpha-scattering interpretation: CBSE 2023 asked for the conclusions Rutherford drew from large-angle scattering (3-marker).
Student Feedback
"The section map helped me figure out where to find the Rydberg formula fast. I scored full marks on the NEET spectral series question." - Class 12 student, Delhi
"Sections 12.4 and 12.5 are essentially the whole chapter for NEET. The breakdown table made it easy to skip 12.1 on the second pass and save time." - NEET 2025 aspirant
Other Resources for Class 12 Physics Chapter 12 Atoms
| Resource | Link |
|---|---|
| NCERT Book PDF | Atoms NCERT PDF |
| NCERT Solutions | Atoms Class 12 Physics NCERT Solutions |
| Notes | Atoms Class 12 Physics Notes |
| Formula Sheet | Atoms Class 12 Physics Formula Sheet |
NCERT Book PDF for Class 12 Physics: All Chapters
Get other Class 12 Physics NCERT Book PDFs as free downloads:
| Chapter | Resource |
|---|---|
| Chapter 1 | Electric Charges and Fields NCERT PDF |
| Chapter 2 | Electrostatic Potential and Capacitance NCERT PDF |
| Chapter 3 | Current Electricity NCERT PDF |
| Chapter 4 | Moving Charges and Magnetism NCERT PDF |
| Chapter 5 | Magnetism and Matter NCERT PDF |
| Chapter 6 | Electromagnetic Induction NCERT PDF |
| Chapter 7 | Alternating Current NCERT PDF |
| Chapter 8 | Electromagnetic Waves NCERT PDF |
| Chapter 9 | Ray Optics and Optical Instruments NCERT PDF |
| Chapter 10 | Wave Optics NCERT PDF |
| Chapter 11 | Dual Nature of Radiation and Matter NCERT PDF |
| Chapter 12 | Atoms NCERT PDF |
| Chapter 13 | Nuclei NCERT PDF |
| Chapter 14 | Semiconductor Electronics NCERT PDF |
Atoms NCERT PDF - Frequently Asked Questions
Ques. Where can I download the Atoms Class 12 Physics NCERT Book PDF?
Ans. Download the Atoms NCERT PDF directly from this page. The 2026-27 edition is the official Part II Chapter 12 PDF and is free.
Ques. Is this Atoms NCERT PDF aligned with the 2026-27 CBSE syllabus?
Ans. Yes. The six sections from 12.1 to 12.6 are retained. The Thomson model history is compressed and the Frank-Hertz description is removed, but the Bohr derivation (12.4) and spectral series (12.5) sections are fully intact.
Ques. How many pages is the Atoms NCERT PDF for Class 12 Physics?
Ans. The Atoms NCERT PDF runs approximately 22 pages. It covers six sections, about 10 solved Examples and 21 end-of-chapter Exercises on Rutherford scattering, the Bohr model and the hydrogen spectral series.
Ques. Which sections in Chapter 12 Atoms are most important for CBSE Boards?
Ans. Sections 12.2 (Alpha-particle scattering), 12.4 (Bohr Model) and 12.5 (Line Spectra of Hydrogen) are the most important. These three sections account for over 80% of CBSE, JEE Main and NEET questions from this chapter.
Ques. Which spectral series of hydrogen lies in the visible region?
Ans. Only the Balmer series lies in the visible region. The Lyman series is in the ultraviolet range. The Paschen, Brackett and Pfund series lie in the infrared range. NCERT states this in Section 12.5 - it is one of the most repeated NEET facts from this chapter.
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