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Radioactivity

Explore the fundamentals of radioactivity, including atomic structure, isotopes, and background radiation. Learn about alpha, beta, and gamma rays, as well as the various uses of radiation in medicine, food preservation, and nuclear power. Discover how nuclear fission works, leading to chain reactions, and the significance of isotopes in determining an element’s properties. Unravel the mysteries of radioactivity and its implications in various fields.

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Radioactivity

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  1. Radioactivity

  2. Contents • Atomic Structure • Isotopes • Background Radiation • Alpha, Beta, Gamma • Uses of Radiation • Nuclear Fission • Chain Reactions

  3. Electron: negative, mass nearly nothing Proton: positive, same mass as neutron (“1”) Neutron: neutral, same mass as proton (“1”) Atomic Structure

  4. Isotopes are the same element with a different mass number. Isotopes have different numbers of neutrons 16 O 17 18 O O 8 8 8 The atomic number controls which element it is. e.g. Oxygen must always have 8 protons Isotopes Radiation occurs when the mass number of an element changes

  5. 13% are man-made Radon gas Food Cosmic rays Gamma rays Medical Nuclear power Background Radiation

  6. Alpha, Beta, Gamma Alpha (α): atom decays into a new atom & emits an alpha particle (2 protons and 2 neutrons: the nucleus of a helium atom) Unstable nucleus New nucleus Alpha particle Beta (β): atom decays into a new atom by changing a neutron into a proton & electron. The fast moving, high energy electron is called a beta particle Beta particle Unstable nucleus New nucleus Gamma (γ): after α or β decay, surplus energy is sometimes emitted. This is called gamma radiation & has a very high frequency with short wavelength. The atom is not changed Unstable nucleus New nucleus Gamma radiation

  7. β passes through paper, card etc. β passed through sheets to a detector When β count slows material is too thick α  γ Uses of Radiation Few cm of lead Sheet of paper Thin foil • γ kills microbes • Medical instruments sterilised • Food keeps fresh for longer • No damage to substances • Half-life short so no radiation afterwards

  8. Nuclear Fission • Nuclear fission occurs when the mass number of an element splits. The product is a new element and released neutrons • Nuclear fission releases heat energy • This heat is harnessed in nuclear power stations to boil water, which is used to drive turbines and machinery • The amount of energy produced by each reaction is very small billions of reactions occur every second • The waste products from these reactions are radioactive, which is why many people worry about nuclear power plants

  9. More neutrons Neutron Unstable nucleus Uranium nucleus Nuclear Fission New nuclei (e.g. barium and krypton)

  10. Chain Reactions • Each fission reaction releases neutrons that are used in further (chain) reactions

  11. Summary • Nucleus = protons and neutrons; electrons are in shells • Isotopes = same element with different mass number • Background radiation = many causes, some man-made • Alpha (highly ionising, low penetration), Beta (stopped by a few mm of foil), Gamma (high penetration  v dangerous) • Uses of radiation (Beta: quality assurance, Gamma: medical instruments & food freshness) • Nuclear fission = atom divides  releases neutrons • Chain reactions = result of released neutrons

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