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Intro to Nuclear Chemistry

Intro to Nuclear Chemistry. Chemistry Mrs. Coyle. http://www.chem.orst.edu/graduate/pics/Reactor.jpg. How does a nuclear reactor work?. http://www.lanl.gov/science/1663/images/reactor.jpg. How does a small mass contained in this bomb cause……. Nuclear Bomb of 1945 known as “fat man”.

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Intro to Nuclear Chemistry

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  1. Intro to NuclearChemistry Chemistry Mrs.Coyle http://www.chem.orst.edu/graduate/pics/Reactor.jpg

  2. How does a nuclear reactor work? http://www.lanl.gov/science/1663/images/reactor.jpg

  3. How does a small mass contained in this bomb cause…… • Nuclear Bomb of 1945 known as “fat man” http://www.travisairmuseum.org/assets/images/fatman.jpg

  4. …this huge nuclear explosion? http://library.thinkquest.org/06aug/01200/Graphics/705px-Nuclear_fireball.jpg

  5. Is there radon in your basement? http://a.abcnews.com/images/Blotter/abc_1radon_ad_070625_ssh.jpg

  6. Notation

  7. Nucleons • Protons and Neutrons

  8. The nucleons are bound together by the strongforce.

  9. Isotopes • Atoms of a given element with: same #protons but different # neutrons

  10. H H H http://education.jlab.org/glossary/isotope.html

  11. Isotopes of Carbon

  12. Radioactive Isotopes • Isotopes of certain unstable elements that spontaneously emit particles and energy from the nucleus. • Henri Beckerel 1896 accidentally observed radioactivity of uranium salts that were fogging photographic film. • His associates were Marie and Pierre Curie.

  13. Marie Curie: born 1867, in Poland as Maria Sklodowska • Lived in France • 1898 discovered the elements polonium and radium. http://www.radiochemistry.org/nuclearmedicine/pioneers/images/mariecurie.jpg

  14. Marie Curie a Pioneer of Radioactivity • Winner of 1903 Nobel Prize for Physics with Henri Becquerel and her husband, Pierre Curie. • Winner of the sole 1911 Nobel Prize for Chemistry.

  15. 3 Main Types of Radioactive Decay • Alpha a • Betab • Gamma g

  16. Alpha Decay Emission of alphaparticlesa : • helium nuclei • two protons and two neutrons • charge +2e  • can travel a few inches through air • can be stopped by a sheet of paper, clothing.

  17. Alpha Decay Uranium Thorium

  18. Alpha Decay http://education.jlab.org/glossary/alphadecay.gif

  19. Beta Decay • Beta particles b: electrons ejected from the nucleus when neutrons decay ( n -> p+ +b- ) • Beta particles have the same charge and mass as "normal" electrons.

  20. Beta Decay • Beta particles b: electrons ejected from the nucleus when neutrons decay n -> p+ +b- • Beta particles have the same charge and mass as "normal" electrons. • Can be stopped by aluminum foil or a block of wood.

  21. Beta Decay

  22. Beta Decay Thorium Protactinium

  23. Gamma Decay • Gamma radiation g : electromagnetic energy that is released.  • Gamma rays are electromagnetic waves. • They have no mass. • Gamma radiation has no charge. • Most Penetrating, can be stopped by 1m thick concrete or a several cm thick sheet of lead.

  24. Examples of RadioactiveDecay Alpha Decay Po  Pb + He Beta Decay p n + e n  p + e C  N + e Gamma Decay Ni  Ni + g (excited nucleus)

  25. Which is more penetrating? Why?

  26. Part II Nuclear Stability Half-Life

  27. Nuclear Stability • Depends on the neutron to proton ratio.

  28. Band of Stability Number of Neutrons, (N) Number of Protons (Z)

  29. What happens to an unstable nucleus? • They will undergo decay • The type of decay depends on the reason for the instability

  30. What type of decay will happen if the nucleus contains too many neutrons? • Beta Decay

  31. Example: 14 14 0 C  N + e In N-14 the ratio of neutrons to protons is 1:1 6 -1 7

  32. Nuclei with atomic number > 83 are radioactive

  33. Radioactive Half-Life (t1/2 ): • The time for half of the radioactive nuclei in a given sample to undergo decay.

  34. Common Radioactive Isotopes Isotope Half-Life Radiation Emitted Carbon-14 5,730 years b, g Radon-222 3.8 days a Uranium-235 7.0 x 108 years a, g Uranium-238 4.46 x 109 years a

  35. Radioactive Half-Life • After one half life there is 1/2 of original sample left. • After two half-lives, there will be 1/2 of the 1/2 = 1/4 the original sample.

  36. Graph of Amount of RemainingNuclei vs Time A=Aoe-lt A

  37. Example You have 100 g of radioactive C-14. The half-life of C-14 is 5730 years. • How many grams are left after one half-life? Answer:50 g • How many grams are left after two half-lives?

  38. Problem A sample of 3x107 Radon atoms are trapped in a basement that is sealed. The half-life of Radon is 3.83 days. How many radon atoms are left after 31 days? answer:1.2x105 atoms

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