Introduction to Nuclear Chemistry

Nuclear chemistry deals with reactions and properties of atomic nuclei. Unlike chemical reactions, which involve electrons, nuclear reactions involve changes in the nucleus of atoms, often producing large amounts of energy.

Understanding nuclear chemistry is important for NEET because it explains radioactivity, nuclear stability, energy production, and medical applications.

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Radioactivity

Radioactivity is the spontaneous emission of particles or radiation from unstable nuclei. It was discovered by Henri Becquerel in 1896 and later studied by Marie and Pierre Curie.

Key Points:

• Only unstable nuclei are radioactive.

• Radioactive decay transforms the parent nucleus into a more stable daughter nucleus.

• Types of natural radioactivity: alpha, beta, and gamma radiation.

Types of Radioactive Decay

1. Alpha Decay (α-decay):

• Emission of an alpha particle (helium nucleus) consisting of 2 protons and 2 neutrons.

• Reduces atomic number by 2 and mass number by 4.

• Example: Uranium-238 decays to Thorium-234.

• Alpha particles are heavy and positively charged, and have low penetration (stopped by paper).

2. Beta Decay (β-decay):

• Emission of a beta particle (electron or positron).

• Beta-minus decay: Neutron → proton + electron + antineutrino

• Beta-plus decay (positron emission): Proton → neutron + positron + neutrino

• Atomic number changes, but mass number remains nearly the same.

• Beta particles have medium penetration (stopped by aluminum sheets).

3. Gamma Decay (γ-decay):

• Emission of electromagnetic radiation from an excited nucleus.

• Does not change atomic or mass number.

• Highly penetrating; requires lead shielding.

NEET Tip: Remember the differences between α, β, and γ radiation in terms of mass, charge, and penetration power.

Half-Life

• Half-life is the time required for half of the radioactive nuclei to decay.

• Conceptually, it measures rate of decay and is independent of initial quantity.

• Important for NEET questions related to radioactive dating, medical isotopes, and decay sequences.

Nuclear Reactions

Nuclear reactions involve changes in the nucleus and may produce new elements. Unlike chemical reactions, they are accompanied by large energy changes.

• Examples: Fission and fusion.

• Key differences from chemical reactions:

  • Mass defect and energy release (E = mc²)

  • Involves nuclear particles (protons, neutrons), not electrons

  • Changes in element identity

Nuclear Fission

• Fission is the splitting of a heavy nucleus into two lighter nuclei along with neutrons and a large amount of energy.

• Example: Uranium-235 fission produces Barium-141, Krypton-92, neutrons, and energy.

• Applications: Nuclear reactors, nuclear weapons.

• Key Concept: Fission can initiate a chain reaction if emitted neutrons strike other nuclei.

Nuclear Fusion

• Fusion is the combining of light nuclei to form a heavier nucleus, releasing enormous energy.

• Example: Fusion of Hydrogen nuclei to form Helium in the Sun.

• Applications: Stars’ energy, potential energy source on Earth.

• Requires extremely high temperatures and pressures.

NEET Tip:

• Fission: Splitting → chain reaction, controlled in reactors

• Fusion: Combining → energy from stars, experimental reactors

Mass Defect and Binding Energy

• Mass defect: Difference between mass of nucleus and sum of individual nucleons’ masses.

• Indicates mass converted to energy (binding energy) according to Einstein’s equation E = mc².

• Binding energy explains nuclear stability:

  • Higher binding energy per nucleon → more stable nucleus

  • Iron-56 is one of the most stable nuclei

Stability of Nuclei

• Stability depends on neutron-to-proton ratio and binding energy.

• Light nuclei: Stable if n/p ≈ 1

• Heavy nuclei: Stable if n/p > 1

• Nuclei outside the stability band are radioactive and decay via α, β, or γ emission.

NEET Tip: Stability concepts help predict type of decay for a given isotope.

Applications of Nuclear Chemistry

1. Medicine:

• Radioisotopes used in diagnosis and treatment (e.g., Iodine-131 for thyroid, Cobalt-60 for cancer therapy).

2. Energy Production:

• Nuclear reactors utilize controlled fission reactions to generate electricity.

3. Agriculture:

• Gamma radiation used for food preservation and mutation breeding.

4. Industry:

• Radioisotopes used in tracing, thickness measurement, and radiography.

5. Environmental:

• Radioactive tracers study pollution pathways and groundwater flow.

Quick Summary Table

Conclusion

Nuclear Chemistry is a crucial chapter for NEET, focusing on radioactivity, types of decay, nuclear reactions, fission, fusion, and applications. Conceptual understanding is more important than calculations, as NEET emphasizes decay types, stability, and real-life applications. Linking nuclear reactions to energy and stability allows students to score high in both theory and reasoning-based questions. StudentBro.in provides structured, conceptual notes to help NEET aspirants grasp nuclear chemistry efficiently and confidently.