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Radioisotopes Introduction to Nuclear Chemistry

Radioisotopes Introduction to Nuclear Chemistry. OBJECTIVES:. Explain what causes an isotope to become unstable. Compare and contrast chemical vs. nuclear reactions. Explain how an unstable nucleus releases energy. Identify the three types of nuclear radiation and their properties.

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Radioisotopes Introduction to Nuclear Chemistry

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  1. RadioisotopesIntroduction to Nuclear Chemistry

  2. OBJECTIVES: • Explain what causes an isotope to become unstable. • Compare and contrast chemical vs. nuclear reactions. • Explain how an unstable nucleus releases energy. • Identify the three types of nuclear radiation and their properties.

  3. ISOTOPES REVIEW Isotopes: Different atoms of the same element that have the same number of protons but different number of neutrons. Examples: Carbon-12, Carbon-13

  4. Two Categories of Isotopes • Unstable – isotopes that continuously and spontaneously break down/decay in other lower atomic weight isotopes • Stable – isotopes that do not naturally decay but can exist in natural materials in differing proportions

  5. What causes isotopes to become unstable? • An unhealthy ratio of neutrons to protons inside of the nucleus. • The most stable ratio of neutrons to protons is 1:1. Ex: Lithium has 6 isotopes; Li-6, Li-7, Li-8, Li-9, Li-10, and Li-11. • Only Li-6 and Li-7 are stable: Li-6 has 3 protons and 3 neutrons; 3 neutrons = 1:1 ratio Li-9 = 6 neutrons = 2:1 ratio 3 protons stable 3 protons unstable • The ratio of neutrons to protons is higher than 1:1; so they are unstable.

  6. Phet Colorado SimulationIsotopes and Atomic Masswww. phet.colorado.edu • Go to the following website: www.phet.colorado.edu • Type in Isotopes and Atomic Masses in the search bar at the top of the page. • When the simulation appears, click on “Isotopes” • Observe the isotopes of hydrogen and lithium, and their stable and unstable isotopes. • Look at Lithium; which isotopes are unstable? Why?

  7. Radioactivity • Was first observed by Marie and Pierre Curie (1900s) using uranium (U) atoms. • Radioactivity: The process by which substances spontaneously emit rays and particles (radiation).

  8. Radioactivity differs from chemical reactions in a number of ways: • In chemical reactions, atoms attain a stable electron configuration by losing/sharing electrons. In nuclear reactions, the nucleus of an unstable isotope gains stability by undergoing changes. • Unlike chemical reactions, nuclear reactions are notaffected by changes in temperature, pressure, or the presence of catalysts. • Nuclear reactions of an isotope cannot be sped up, slowed down, or turned off

  9. Radioactivity • Unstable radioactive isotopes (radioisotopes) are transformed into stable (nonradioactive) isotopes of a different element. • Radioactive decay: is the process by which an unstable nucleus releases energy by emitting radiation in the form of alpha, beta, or gamma decay.

  10. Types of Radiation • 1. Alpha Radiation • 2. Beta Radiation • 3. Gamma Radiation

  11. Alpha (α) Radiation • Recall, Rutherford used alpha particles to discover the nucleus in his Gold Foil Experiment • Usually written as α or 42He. • Due to its large mass and charge, alpha particles do not travel very far. • They cannot penetrate very well – a sheet of paper or the surface of your skin stops them. • However, they are toxic when ingested.

  12. Alpha (α) Radiation Example:Alpha decay of Uranium-238 238 92 234 90 4 2 U Th He + Radioactive decay

  13. Alpha Decay

  14. Beta (β) Radiation • Results from the breaking apart of a neutron into a proton and an electron (beta particle). • Usually written as: 0-1e or β • Has much less mass than an alpha particle and can therefore penetrate more easily. • Can pass through paper, but is stopped by foil or wood.

  15. Beta (β) Radiation Example:Beta decay of Carbon-14 14 6 14 7 0 ----1- C N e Radioactive decay +

  16. Beta Decay Thorium Protactinium

  17. Gamma (γ) Radiation • A high energy photon emitted by a radioisotope. • Usually written as: 00γ or γ • Often emitted with alpha or beta particles during radioactive decay. • Gamma rays are electromagnetic waves • Has no mass or charge. • Extremely penetrating and can be very dangerous. • Easily passes through paper, wood, and the human body. • Penetration can be stopped, although not completely, by several centimeters of lead.

  18. Gamma (γ) Radiation Example:Gamma/alpha emission from Thorium-230 230 90 226 88 4 2 Th Rn He γ + + Radioactive decay

  19. CLASSWORK / HOMEWORK • Type an ½ page essay listing and explaining the benefits and dangers of radioisotopes. • Due tomorrow

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