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Discovering Radioactivity: Types and Detection Methods

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This chapter explores the discovery of radioactivity by Henri Becquerel in 1896 and its subsequent analysis by Marie Curie. Radioactivity is defined as the spontaneous emission of radiation from unstable atomic nuclei. It discusses the types of radiation: alpha, beta, and gamma, highlighting their properties, charges, and penetration abilities. Additionally, the chapter covers nuclear reactions, the changes in elemental identity due to proton and neutron gain or loss, and methods for detecting radioactivity, such as photographic film and Geiger counters.

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Discovering Radioactivity: Types and Detection Methods

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  1. NUCLEAR CHEMISTRY CHAPTER 21.1 Types of Radioactivity

  2. Discovery of Radioactivity • Radiation: Energy that is spontaneously released from, or given off, by an object • Accidentally discovered by Henri Becquerel in 1896 • Becquerel was studying a phosphorescent uranium compound when he discovered that it gave off, what he thought, was radiation. • To verify his hypothesis he sent his work to Marie Curie • Curie concluded that a nuclear reaction was occurring inside the uranium atoms because it had an unstable nucleus

  3. Radioactivity • Definition: the spontaneous emission of energy/radiation by an unstable atomic nucleus • Radioactive elements • Uranium • Plutonium • Radium • Radon • Curium

  4. Nuclear Reactions • During a nuclear reaction a nucleus can gain or lose protons and neutrons • What would happen if you gained or lost protons? • The identity of the element would change. • You can represent nuclear reactions with equations REACTANTS PRODUCTS PARENT ELEMENT DAUGHTER ELEMENT

  5. Types of Radiation • Alpha radiation • Consist of alpha particles. (α) • Helium nuclei being emitted from the nucleus U Th + He Uranium-238  Thorium-234 + Alpha particle • Do not travel far due to large mass (most massive of the particles) • Are not very penetrating- easily stopped by skin or paper • Only dangerous if ingested • Has a +2 charge • Symbol: 42 He

  6. Types of Radiation • Beta Radiation • Consist of beta particles (β) • Fast moving electrons formed by the decomposition of a neutron in an atom. N  H + e Neutron  proton + electron (beta particle) • The neutron decomposes into a proton, which remains in the nucleus, and an electron, which is released from the atom • Charge of -1 • These are more penetrating because they have less charge and less mass • Stopped by aluminum foil or thin pieces of wood • Symbol: 0-1e

  7. Types of Reactions • Gamma Radiation • Consist of gamma rays (ϒ) • High energy form of radiation because has no mass or charge • Penetrates almost everything and can seriously harm living cells • Can be stopped by thick blocks of lead or thicker blocks of concrete • Symbol:00Υ

  8. How far can they go?

  9. Detecting Radioactivity • Radioactivity cannot be seen, heard, smelled, tasted, or touched….so how do we know its there? • Photographic film • If the source of radioactivity is nearby • People who work near radiation wear film badges showing their exposure levels • Geiger counter • An instrument that senses radioactive particles

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