2.2 Radioactivity and Stability of Isotopes

• Stability of isotopes; radioactive decay
• Types and properties of radiations: nature, charge, mass, penetration, ionising power, behaviour in fields
• Detection of radiations; safety precautions
• Half-life and its significance
• Nuclear equations and chain reactions
• Nuclear fission and fusion
• Medical and industrial applications of radioactivity

• explain the terminologies used in radioactivity
• identify the types and properties of radioactive emissions in nature
• illustrate how radionuclides attain their stability using nuclear equations
• demonstrate the detection of radioactive emissions in nature
• determine the half-life of common radioactive elements
• appreciate the applications and safety precautions of radioactivity in real life

“What are the risks of exposure to radiation?”

“How can the age of a wooden object thousands of years old be determined?”

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1. The unstable nucleus and its radiations
   40 min · 2 practice tasks · quiz
   Why some nuclei fall apart on their own, and the three things they throw out when they do.
2. Nuclear equations and half-life
   40 min · 2 practice tasks · quiz
   Writing down what a decay does to a nucleus, and measuring how fast a sample disappears.
3. Fission, fusion, applications and safety
   40 min · 2 practice tasks · quiz
   Splitting and joining nuclei, what radioactivity is used for, and how to work with it safely.
4. The nucleus and its nucleons
   40 min · 1 practice tasks · quiz
   Protons, neutrons, A and Z, and how a nuclide is written.
5. Isotopes of the same element
   40 min · 1 practice tasks · quiz
   Same Z, different N: why carbon-12 and carbon-14 are both carbon, and why one decays.
6. The neutron-to-proton ratio
   40 min · 1 practice tasks · quiz
   Why light nuclei like N ≈ Z, and why heavy nuclei need extra neutrons.
7. The strong force and why large nuclei fail
   40 min · 1 practice tasks · quiz
   Short-range attraction versus long-range proton repulsion.
8. Alpha radiation close up
   40 min · 1 practice tasks · quiz
   A helium nucleus: charge, mass, range, and what it does to A and Z.
9. Beta particles from the nucleus
   40 min · 1 practice tasks · quiz
   A neutron becomes a proton plus an electron; Z rises, A does not.
10. Gamma rays: energy only
    40 min · 1 practice tasks · quiz
    No mass, no charge, A and Z unchanged; the most penetrating emission.
11. Ionisation against penetration
    40 min · 1 practice tasks · quiz
    One property explains both: frequent collisions ionise strongly and stop the particle soon.
12. Alpha, beta and gamma in fields
    40 min · 1 practice tasks · quiz
    Electric and magnetic fields sort the three radiations by charge.
13. The Geiger–Müller tube
    40 min · 1 practice tasks · quiz
    How a GM tube turns ionisation into a countable click, including background.
14. Film, cloud chamber and electroscope
    40 min · 1 practice tasks · quiz
    Three other detectors, each still using ionisation.
15. Background radiation in Kenya
    40 min · 1 practice tasks · quiz
    Rocks, radon, cosmic rays, food and a little medicine — always there, always subtracted.
16. Writing nuclear equations
    40 min · 1 practice tasks · quiz
    Conserve A and Z, then the product identifies itself.
17. Decay series until stability
    40 min · 1 practice tasks · quiz
    One decay is rarely enough; chains end at lead, and radon sits in the middle.
18. Half-life is a constant
    40 min · 1 practice tasks · quiz
    The time for half the nuclei to decay never changes, and the sample never quite reaches zero.
19. Half-life calculations
    40 min · 1 practice tasks · quiz
    Count the halvings, or divide the time by t½, then apply (½)^n.
20. Decay curves and background
    40 min · 1 practice tasks · quiz
    Subtract background, plot a smooth curve, read off successive half-lives.
21. Modelling half-life with dice and a burette
    40 min · 1 practice tasks · quiz
    A random process with a fixed chance per throw (or drop) makes an exponential curve.
22. Carbon-14 dating of wood and bone
    40 min · 1 practice tasks · quiz
    Living things keep a steady C-14 fraction; after death the fraction only falls.
23. Fission, fusion and control
    40 min · 1 practice tasks · quiz
    Splitting heavy nuclei, joining light ones, and holding a chain to one neutron each time.
24. Hospitals, mines and safety in Kenya
    40 min · 1 practice tasks · quiz
    Radiotherapy and tracers, radon in mines, waste, and the three safety rules.