Lecture on Nuclear Reactions

Introduction

• Electromagnetic Force: Responsible for chemical phenomena.
  • Atoms form due to attraction between protons and electrons.
  • Leads to chemical bonds, enzyme recognition, DNA base pairing.
• Four Fundamental Forces:
  • Gravity: Weakest, operates on astronomical distances (planets, stars, galaxies).
  • Electromagnetism: Causes chemistry, operates on scale of atoms and molecules.
  • Strong Nuclear Force: Keeps the nucleus together, operates on atomic nuclear scale.
  • Weak Nuclear Force: Facilitates nuclear decay, causes transmutation of elements.

Nuclear Reactions

• Chemical Reactions: Involving valence electrons, identity of atoms unchanged.
• Nuclear Reactions: Change occurs in the nucleus, atoms change from one element to another.
  • Discovered by Henri Becquerel in 1896.
  • Types of particles:
    • Alpha Particle: Helium nucleus (2 protons, 2 neutrons).
    • Beta Particle: Electron.
    • Positron: Antimatter counterpart of the electron.
    • Gamma Particle: Photon of light, electromagnetic radiation.

Writing Nuclear Reactions

• Notation of particles:
  • Lower number = atomic number (protons).
  • Upper number = atomic mass (protons + neutrons).
  • Proton: p, mass 1, atomic number 1.
  • Neutron: n, mass 1, atomic number 0.
  • Alpha: He or α, mass 4, atomic number 2.
  • Electron: e or β, mass ~0, atomic number -1.
  • Positron: mass ~0, atomic number 1.
  • Photon: γ, mass 0, atomic number 0.
• Arithmetic for resulting nucleus:
  • Atomic numbers and mass numbers must add up to the same on both sides of the reaction.

Causes of Nuclear Instability

• Too Large Nucleus: Strong nuclear force too weak over large distance, causes alpha emission or spontaneous fission.
• Nucleon Numbers: Ideal numbers create stability (magic numbers).
• Proton-Neutron Ratio: 1:1 for small atoms, up to 1.5:1 for large atoms.
  • Too many protons: Positron emission or electron capture.
  • Too many neutrons: Beta emission.
  • Excited state: Gamma emission.

Types of Decay

• Alpha Emission: Reduces size of the nucleus.
• Beta Emission: Neutron transforms to proton, emits electron and antineutrino.
• Positron Emission: Proton transforms to neutron, emits positron and neutrino.
• Electron Capture: Proton becomes neutron by absorbing an electron.
• Gamma Emission: Emits high-energy gamma photon.

Radioactive Decay

• Decay Series: Series of decays leading to a stable nucleus.
• Radiation Effects: High-energy particles can damage DNA, causing mutations.
• Half-Life: Time for half the original material to decay.

Harnessing Nuclear Energy

• E=mc²: Matter converted to energy.
  • Nuclear Fission: Splitting of unstable nuclei, chain reactions.
  • Nuclear Fusion: Fusion of small nuclei, more powerful than fission, promises renewable energy solutions.

Conclusion

• Power of nuclear reactions and importance in energy production.
• Potential role in advancements of technology.