Introduction to Atomic and Nuclear Physics

The chapter Atomic and Nuclear Physics is a vital part of NEET Physics under modern physics. It explains the structure of atoms, nuclear properties, radioactivity, and nuclear reactions.

This chapter is important for NEET aspirants because it combines conceptual understanding, experimental insights, and formula-based calculations, which are frequently tested in both theory and numericals.

StudentBro notes provide exam-focused explanations, step-by-step derivations, and solved examples for mastery.

Direct Links to Download 2025-26 Physics Notes (PDF)

► Click “Download Here” next to your subject to access the free PDF.

Structure of Atom

• Atoms consist of nucleus (protons and neutrons) and electrons orbiting around it

• Atomic number (Z): Number of protons in the nucleus

• Mass number (A): Number of protons + neutrons

• Isotopes: Same Z, different A

• Isobars: Same A, different Z

• Isotones: Same number of neutrons, different Z

• NEET conceptual questions may ask differences and examples of isotopes, isobars, and isotones.

Bohr’s Model of Atom

• Postulates:

  1. Electrons revolve around the nucleus in stable orbits without emitting radiation

  2. Energy is quantized; emission occurs only when electrons jump between orbits

  3. Angular momentum L = nħ (n = 1, 2, 3 …)

• Energy of electron in nth orbit: E_n = -13.6 eV / n²

• Radius of orbit: r_n = n² × a₀ / Z

• NEET numericals include calculating energy levels, spectral lines, and orbital radii.

Spectral Lines and Rydberg Formula

• Hydrogen Spectrum: Lyman, Balmer, Paschen series

• Rydberg Formula: 1/λ = R (1/n₁² − 1/n₂²)

• R = 1.097 × 10⁷ m⁻¹ (Rydberg constant)

• NEET may ask wavelengths of spectral lines, transitions, and series identification.

Radioactivity

• Definition: Spontaneous emission of particles or radiation from unstable nuclei

• Types of Radiation: Alpha (α), Beta (β), Gamma (γ)

• Half-Life (T₁/₂): Time in which half of radioactive nuclei decay

• Decay Constant (λ): λ = 0.693 / T₁/₂

• Activity (A): A = λN

• NEET numericals often include calculating decay, half-life, and activity.

Nuclear Reactions

• Definition: Reactions involving change in nucleus composition

• Types:

  1. Fission – Splitting of heavy nuclei, releases large energy

  2. Fusion – Combining light nuclei, releases energy

• Mass-Energy Equivalence: E = Δm c²

• NEET questions may ask energy released in fission or fusion reactions.

Binding Energy of Nucleus

• Definition: Energy required to break a nucleus into its constituent nucleons

• Formula: BE = Δm c²

• Significance: Determines stability of nuclei

• NEET numericals often involve calculating binding energy per nucleon and stability of nuclei.

Mass Defect

• Definition: Difference between mass of nucleus and sum of masses of protons and neutrons

• Δm = (Z m_p + N m_n − m_nucleus)

• Relation to Binding Energy: BE = Δm c²

• NEET may ask calculations involving mass defect and energy released in nuclear reactions.

Nuclear Fission and Fusion Applications

1. Nuclear Fission: Power plants, atomic bombs

2. Nuclear Fusion: Sun’s energy, hydrogen bomb

3. Radiotherapy: Cancer treatment using radioisotopes

4. Radioisotopes in Medicine and Industry: Tracers, diagnostics, and sterilization

• NEET conceptual questions often ask applications of nuclear reactions in real life.

Important Formulas for NEET

1. Energy levels in hydrogen: E_n = -13.6 / n² eV

2. Radius of Bohr orbit: r_n = n² × a₀ / Z

3. Rydberg formula: 1/λ = R (1/n₁² − 1/n₂²)

4. Decay constant: λ = 0.693 / T₁/₂

5. Activity: A = λN

6. Binding energy: BE = Δm c²

7. Mass defect: Δm = Z m_p + N m_n − m_nucleus

• Mastery of these formulas is crucial for solving numerical problems in NEET.

Tips for NEET Preparation on Atomic and Nuclear Physics

1. Memorize Bohr model formulas, spectral series, half-life, decay constant, and binding energy formulas

2. Understand radioactive decay and nuclear reactions

3. Relate concepts to practical applications in medicine, energy, and industry

4. Practice numericals involving energy levels, decay, mass defect, and binding energy

5. Visualize atomic and nuclear structures using diagrams

StudentBro notes include step-by-step derivations, experimental illustrations, and solved numerical examples for conceptual clarity.

Advantages of StudentBro NEET Physics Notes

• Covers Bohr model, spectral lines, radioactivity, nuclear reactions, binding energy, and mass-energy equivalence

• Includes step-by-step derivations, solved examples, and real-life applications

• Structured for easy revision and conceptual clarity

• Focused on NEET syllabus and high-yield questions

These notes ensure aspirants can confidently tackle atomic and nuclear physics questions in NEET exams.

Conclusion

The chapter Atomic and Nuclear Physics is a crucial part of NEET Physics under modern physics. Mastery of Bohr’s model, spectral lines, radioactivity, half-life, binding energy, and nuclear reactions is essential for solving both conceptual and numerical problems.

StudentBro NEET Physics notes provide structured, clear, and exam-focused guidance, enabling aspirants to confidently solve atomic and nuclear physics questions and excel in NEET exams.