Get the Atoms NCERT PDF below, freshly aligned to the 2026-27 CBSE syllabus revision. The Atoms NCERT PDF on this page is the official NCERT Part-II chapter for Atoms, with every section retained after the latest NCERT rationalisation. Use the Atoms NCERT PDF alongside the section map and 4-mark weightage chart further down.
- CBSE Weightage: 3 to 4 marks
- JEE Main Weightage: 2 to 3% (1 question per paper)
- NEET Weightage: 2 to 3 questions per year
Both downloads of the Atoms NCERT PDF on this page are free and updated for the 2026-27 NCERT syllabus.
This NCERT Book PDF page is curated by subject experts, mapped to the 2026-27 NCERT, and refined against the last five years of CBSE Board, JEE Main, and NEET papers.
How will the Atoms NCERT PDF on Collegedunia Help You?
The Atoms chapter is short but front-loaded with high-yield questions.
- 2026-27 NCERT Alignment: The PDF is the latest edition, with the six-section structure (12.1 to 12.6) preserved.
- Section-by-Section Reading Map: Each section is tagged with a page range so you know exactly where Bohr's postulates or the Rydberg formula sits.
- Example and Exercise Inventory: All 10 intext Examples and 21 Exercises are mapped to sub-topics.
- Study Plan and Reading Order: A 2-day plan and a Modern-Physics cluster reading order tell you when to read this chapter.
Atoms Video Chapter Walkthrough
Source: Next Toppers - 12th Science on YouTube
Atoms NCERT Section-by-Section Breakdown for Class 12 Physics
The chapter has six sections covering roughly 22 pages. The table maps each section to its page range and core idea.
| 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. |
Sections 12.2, 12.4 and 12.5 carry almost the entire exam yield. A focused reader can extract over 80% of the question bank from just these three sections.
Atoms Intext Example Inventory for Class 12 Physics Chapter 12
NCERT places roughly 10 solved Examples through the chapter. Each one is a single-step or two-step numerical the board paper often rephrases verbatim.
| 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 ends with 21 numbered Exercises. Spectral series Exercises (12.5, 12.7, 12.13) and Bohr-radius Exercises (12.10, 12.11) are the most frequently rephrased into CBSE and NEET papers.
Atoms 2026-27 NCERT Edition Note (What Kept, What Dropped)
The current 2026-27 NCERT print retains Chapter 12 Atoms with all six sections intact. The Thomson model history has been compressed to a single introductory paragraph in 12.1, and the detailed Frank-Hertz description has been dropped. The Bohr derivation (12.4) and spectral series derivation (12.5) remain in full.
Full version: the Collegedunia Atoms Class 12 Physics Notes explain each retained sub-topic with derivations and solved numericals.
How to Read the Atoms NCERT PDF (Pass-Sequence Plan)
The chapter is short enough to finish in three reading passes.
- Pass 1 (skim, 25 min): Read Sections 12.1 to 12.3 in full. Skim 12.4 for the three postulates.
- Pass 2 (detailed, 60 min): solve every derivation in 12.4 with a pen. Note rn , vn , En . Derive the Rydberg form yourself.
- Pass 3 (problem-solving, 45 min): Solve all 10 Examples, then attempt Exercises 12.5, 12.7, 12.10 and 12.13.
Also Check:
Atoms Multi-Day Study Plan for the 22-Page NCERT Chapter
The 22-page chapter is small enough to finish over two focused study days. The split below assigns each day a specific set of sections, Examples and 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 |
Day 1 secures Bohr's postulates and derivation. Day 2 converts the Rydberg formula into automatic recall, the highest-yield skill for NEET and JEE Atoms questions.
Cross-Chapter Reading Order for the Modern Physics Cluster
Atoms sits inside a three-chapter Modern Physics cluster. The photon idea from Chapter 11 directly powers Bohr's third postulate, so order matters.
| Order | Chapter | What it sets up for Atoms |
|---|---|---|
| Read first | Chapter 11 Dual Nature of Radiation and Matter | Photon energy E = hν and De Broglie wavelength λ = h/mv . Both are reused in Sections 12.4 and 12.6. |
| Read second | Chapter 12 Atoms (this chapter) | Applies photon and matter-wave ideas to derive discrete orbits and the hydrogen spectrum. |
| Read third | Chapter 13 Nuclei | Extends the nuclear model introduced in Section 12.2 to nuclear radius, binding energy and decay. |
If you read Chapter 12 before Chapter 11, the De Broglie derivation in Section 12.6 will feel unmotivated. Order matters more than time spent in the Modern Physics cluster.
Related Links:
Atoms Top 5 Formulae You Need from the NCERT Chapter
Five formulae cover almost every numerical in the Examples, Exercises and the last 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 10.2 eV) |
Full master table: the Collegedunia Atoms Class 12 Physics Formula Sheet.
Atoms Previous Year Trends from the NCERT Chapter
Three trends repeat across CBSE, JEE and NEET.
- 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.
- 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).
Full year map: Atoms Class 12 Physics NCERT Solutions.
More Atoms Physics Class 12 Resources
NCERT Book PDF for Class 12 Physics: All Chapters
Other Class 12 Physics NCERT Book PDFs you can grab 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 13 | Nuclei NCERT PDF |
| Chapter 14 | Semiconductor Electronics NCERT PDF |
Atoms NCERT PDF: available above as a free PDF download, fully aligned to the 2026-27 NCERT release.
Atoms NCERT PDF - Frequently Asked Questions
Ques. Where can I download Atoms Class 12 Physics NCERT Book PDF?
Ans. You can download the Atoms NCERT PDF directly from this page. The 2026-27 edition is the official Part II Chapter 12 PDF and is free to download.
Ques. Is this Atoms NCERT PDF aligned with the 2026-27 CBSE syllabus?
Ans. Yes. This page reflects the current 2026-27 syllabus for Class 12 Physics. The six sections from 12.1 to 12.6 are retained, with light trims to the Thomson model history and the Frank-Hertz description carried forward from the earlier revision.
Ques. How many pages is the Class 12th Physics Atoms NCERT Book PDF?
Ans. The Atoms NCERT PDF NCERT Book PDF runs approximately 22 pages and covers six sections, 10 solved Examples and 21 end-of-chapter Exercises spanning Rutherford scattering, the Bohr model and the hydrogen spectral series.
Ques. What are the most important sections in the Atoms NCERT chapter for CBSE Boards?
Ans. Sections 12.2 (Alpha-particle scattering and Rutherford's nuclear model), 12.4 (Bohr Model of the Hydrogen Atom) and 12.5 (Line Spectra of Hydrogen) are the most important. These three sections account for over 80% of CBSE Board, JEE Main and NEET questions from this chapter.
Ques. How many intext Examples and Exercises does Chapter 12 Atoms have?
Ans. The chapter contains about 10 solved intext Examples interspersed in the body and 21 numbered end-of-chapter Exercises. Examples 12.5 to 12.8 and Exercises 12.5, 12.7 and 12.13 are the most frequently rephrased into board and entrance papers.
Ques. Which spectral series of hydrogen lies in the visible region according to the NCERT?
Ans. Only the Balmer series lies in the visible region. The Lyman series is in the ultraviolet range, while the Paschen, Brackett and Pfund series lie in the infrared range. NCERT states this explicitly in Section 12.5, and it is one of the most repeated NEET facts.
Ques. Is the NCERT Book PDF alone enough for the Atoms chapter for JEE and NEET?
Ans. For NEET, the NCERT Book PDF along with the NCERT Exemplar is generally sufficient because the question style stays close to the Atoms NCERT PDF. For JEE Main, NCERT covers the concepts fully, but additional practice on hydrogen-like ions and De Broglie wavelength in the nth orbit from HC Verma or DC Pandey is recommended.
Ques. What order should I read the Modern Physics chapters in?
Ans. Read Chapter 11 (Dual Nature of Radiation and Matter) first, then Chapter 12 Atoms NCERT PDF, then Chapter 13 Nuclei. Chapter 11 sets up the photon and De Broglie wavelength ideas that Section 12.4 and Section 12.6 rely on directly.
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