Radioactive decay

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Radioactive decay

  1. 1. <ul><li>The unstable nucleus of a radioactive isotope can spontaneously decompose (break apart). </li></ul><ul><li>It has undergone ‘ radioactive decay ’ </li></ul><ul><ul><li>alpha decay: emitting an alpha particle (a helium nucleus) </li></ul></ul><ul><ul><li>α particle = 4 2 He </li></ul></ul><ul><ul><li>beta decay: emitting a beta particle (an electron particle from the nucleus) </li></ul></ul><ul><ul><li>β particle = 0 -1 e </li></ul></ul><ul><ul><li>gamma decay: emitting electromagnetic radiation </li></ul></ul><ul><ul><li>Ϫ particle = 0 0 Ϫ </li></ul></ul>Radioactive Decay
  2. 2. Summary of Properties intensity decreases by 10% by 3 cm of lead stopped by 12 cm of air or several mm of paper stopped by 4 cm of air or a sheet of paper penetrating ability 1 u 0 0 4 u mass 0 0 1- 2+ charge 1 0 n high energy radiation 0 -1 e electron 4 2 He nucleus nature of radiation neutron (n) Gamma ( Ϫ ) Beta ( β ) Alpha ( α ) Property
  3. 3. Balancing Nuclear Equations <ul><li>The sums of the atomic numbers on both sides of the equation must be equal. </li></ul><ul><li>The sums of the mass numbers on both sides of an equation must be equal. </li></ul><ul><li>238 92 U -> 234 90 Th + 4 2 He </li></ul><ul><li>The sums of atomic numbers on both sides of the equation are the same (92 = 90 + 2) </li></ul><ul><li>The sums of the mass numbers on both sides of the equation are the same (238 = 234 + 4) </li></ul>
  4. 4. <ul><li>Write an equation for the emission of an alpha particle from 226 88 Ra </li></ul><ul><li>226 88 Ra -> </li></ul>
  5. 5. <ul><li>Write an equation for the emission of an alpha particle from 226 88 Ra </li></ul><ul><li>226 88 Ra -> 4 2 He + </li></ul>
  6. 6. <ul><li>Write an equation for the emission of an alpha particle from 226 88 Ra </li></ul><ul><li>226 88 Ra -> 4 2 He + 222 86 ___ </li></ul>
  7. 7. <ul><li>Write an equation for the emission of an alpha particle from 226 88 Ra </li></ul><ul><li>226 88 Ra -> 4 2 He + 222 86 Rn </li></ul>
  8. 8. Beta Decay <ul><li>Some unstable nuclei may emit an electron from the nucleus </li></ul><ul><li> 234 90 Th -> 234 91 Pa + 0 -1 e </li></ul><ul><ul><li>sum of mass numbers: 234 = 234 + 0 </li></ul></ul><ul><ul><li>sum of atomic numbers: 90 = 91 – 1 </li></ul></ul><ul><li>Thorium appears to have gained a proton! </li></ul><ul><li>one of the neutrons in Th-234 decomposed into a proton and a neutron </li></ul><ul><li>1 0 n -> 1 1 p + 0 -1 e </li></ul>
  9. 9. <ul><li>Write an equation for the emission of a beta particle from 214 82 Pb </li></ul><ul><li>214 82 Pb -> </li></ul>
  10. 10. <ul><li>Write an equation for the emission of a beta particle from 214 82 Pb </li></ul><ul><li>214 82 Pb -> 0 -1 e + </li></ul>
  11. 11. <ul><li>Write an equation for the emission of a beta particle from 214 82 Pb </li></ul><ul><li>214 82 Pb -> 0 -1 e + 214 83 ___ </li></ul>
  12. 12. <ul><li>Write an equation for the emission of a beta particle from 214 82 Pb </li></ul><ul><li>214 82 Pb -> 0 -1 e + 214 83 Bi </li></ul>
  13. 13. Artificial Transmutation <ul><li>Alchemists never did turn lead into gold, but along the way made many other discoveries about elements and compounds. This was the origin of the science of chemistry! </li></ul><ul><li>In artificial transmutation, a nucleus is hit by a small nuclear particle moving at very high speed. This can produce atoms with a desired number of protons and neutrons. </li></ul><ul><li>27 13 Al + 4 2 He   -> 30 15 P + 1 0 n </li></ul><ul><li>We can now turn lead into gold!         </li></ul>

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