Lecture 25.2- Nuclear Transformations


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Section 25.2 Lecture for Honors & Prep

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Lecture 25.2- Nuclear Transformations

  1. 1. BELLWORK <ul><li>What is the symbol for an alpha particle? </li></ul><ul><li>Write the nuclear equation for the alpha decay of Uranium-238. </li></ul><ul><li>What is the symbol of a beta particle? </li></ul><ul><li>Write the nuclear equation for the beta decay of Carbon-14. </li></ul><ul><li>Write the symbol for gamma radiation. </li></ul><ul><li>Why is gamma radiation often not included in a nuclear equation? </li></ul>
  2. 2. Damage from nuclear radiation is due to ionization of living tissue. <ul><li>Nuclear radiation is called ionizing radiation because it produces ions from neutral molecules. </li></ul><ul><li>Alpha radiation has a low penetration, but it is the most damaging to living tissue because it deposits all its energy along a short path </li></ul>
  3. 3. Lecture 25.2- Nuclear Transformations <ul><li>Radon-222 is a radioactive isotope that is present naturally in the soil in some areas. It has a constant rate of decay. You will learn about decay rates of radioactive substances. </li></ul>25.2
  4. 4. The nucleus is held together by the strong nuclear force <ul><li>The strong nuclear force is the strongest force known </li></ul><ul><li>Protons and neutrons are very close together </li></ul><ul><li>They exchange a teeny bit of mass back and forth. </li></ul><ul><li>When disrupted, the mass is converted to energy according to </li></ul><ul><li>E=mc 2 </li></ul><ul><li>The mass is tiny. </li></ul><ul><li>The energy is immense. </li></ul>
  5. 5. Protons and neutrons experience the strong nuclear force if close enough Because protons repel each other the nucleus needs a certain proton to neutron ratio for stability
  6. 6. <ul><ul><ul><li>More than 1,500 different nuclei are known. Of those, only 264 are stable and do not decay or change with time. These nuclei are in a region called the band of stability . </li></ul></ul></ul>25.2
  7. 7. Nuclear Stability and Decay <ul><ul><ul><li>The neutron-to-proton ratio determines the type of decay that occurs. </li></ul></ul></ul>25.2
  8. 8. <ul><ul><ul><li>A half-life (t 1/2 ) is the time required for one-half of the nuclei of a radioisotope sample to decay to products. </li></ul></ul></ul><ul><ul><ul><ul><li>After each half-life, half of the existing radioactive atoms have decayed into atoms of a new element . </li></ul></ul></ul></ul>25.2
  9. 9. 25.2
  10. 10. 25.2
  11. 11. 25.2 Stable Isotope
  12. 12. <ul><ul><ul><li>The ratio of Carbon-14 to stable carbon in the remains of an organism changes in a predictable way that enables the archaeologist to obtain an estimate of its age. </li></ul></ul></ul>25.2
  13. 13. 25.1
  14. 14. 25.1
  15. 15. 25.1
  16. 16. 25.1
  17. 17. for Sample Problem 25.1
  18. 18. <ul><ul><ul><li>The conversion of an atom of one element to an atom of another element is called transmutation . </li></ul></ul></ul><ul><ul><ul><ul><li>Transmutation can occur by radioactive decay. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Or </li></ul></ul></ul></ul><ul><ul><ul><ul><li>when particles bombard the nucleus of an atom. </li></ul></ul></ul></ul>25.2
  19. 19. <ul><ul><ul><li>The first artificial transmutation reaction involved bombarding nitrogen gas with alpha particles. </li></ul></ul></ul>25.2
  20. 20. <ul><ul><ul><li>The elements in the periodic table with atomic numbers above 92, the atomic number of uranium, are called the transuranium elements. </li></ul></ul></ul><ul><ul><ul><ul><ul><li>All transuranium elements undergo transmutation. </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>None of the transuranium elements occur in nature, and all of them are radioactive. </li></ul></ul></ul></ul></ul>25.2
  21. 21. <ul><ul><ul><li>Transuranium elements are synthesized in nuclear reactors and nuclear accelerators. </li></ul></ul></ul>25.2
  22. 22. 25.2 Section Quiz. <ul><ul><li>1. During nuclear decay, if the atomic number decreases by one but the mass number is unchanged, the radiation emitted is </li></ul></ul><ul><ul><ul><li>a positron. </li></ul></ul></ul><ul><ul><ul><li>an alpha particle. </li></ul></ul></ul><ul><ul><ul><li>a neutron. </li></ul></ul></ul><ul><ul><ul><li>a proton. </li></ul></ul></ul>
  23. 23. 25.2 Section Quiz. <ul><ul><li>2. When potassium-40 (atomic number 19) decays into calcium-40 (atomic number 20), the process can be described as </li></ul></ul><ul><ul><ul><li>positron emission. </li></ul></ul></ul><ul><ul><ul><li>alpha emission. </li></ul></ul></ul><ul><ul><ul><li>beta emission. </li></ul></ul></ul><ul><ul><ul><li>electron capture. </li></ul></ul></ul>
  24. 24. 25.2 Section Quiz. <ul><ul><li>3. If there were 128 grams of radioactive material initially, what mass remains after four half-lives? </li></ul></ul><ul><ul><ul><li>4 grams </li></ul></ul></ul><ul><ul><ul><li>32 grams </li></ul></ul></ul><ul><ul><ul><li>16 grams </li></ul></ul></ul><ul><ul><ul><li>8 grams </li></ul></ul></ul>
  25. 25. 25.2 Section Quiz. <ul><ul><li>4. When transmutation occurs, the ________ always changes. </li></ul></ul><ul><ul><ul><li>number of electrons </li></ul></ul></ul><ul><ul><ul><li>mass number </li></ul></ul></ul><ul><ul><ul><li>atomic number </li></ul></ul></ul><ul><ul><ul><li>number of neutrons </li></ul></ul></ul>
  26. 26. 25.2 Section Quiz <ul><ul><li>5. Transmutation occurs by radioactive decay and also by </li></ul></ul><ul><ul><ul><li>extreme heating. </li></ul></ul></ul><ul><ul><ul><li>chemical reaction. </li></ul></ul></ul><ul><ul><ul><li>high intensity electrical discharge. </li></ul></ul></ul><ul><ul><ul><li>particle bombardment of the nucleus. </li></ul></ul></ul>