Unit 18: Radioactivity - Revision Sheet

1. 📌 Essentials

• Atom: smallest unit matter; consists of nucleus and electrons. -’s experiment: α-particles mostly pass; some deflected, revealing nucleus.
• Nucleus: dense, positively charged core containing protons and neutrons.
• Proton number (Z): defines the element; unique for each element.
• Isotopes: same Z, different A (mass number); e.g., hydrogen isotopes.
• Radioactive decay: spontaneous emission of α, β, or γ radiation.
• Half-life (T₁/₂): time for half the radioactive sample to decay.
• Types of radiation:
  • α: helium nucleus, high ionization, short range.
  • β: electrons, moderate ionization, longer range.
  • γ: electromagnetic waves, low ionization, high penetration.
• Nuclear fission: splitting of heavy nucleus into lighter nuclei + energy.
• Nuclear fusion: combining light nuclei to form heavier nuclei + energy.
• Hazards: burns, mutations, leukemia; require safety precautions.

2. 🧩 Key Structures & Components