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Radioactivity and Nuclear Energy

Radioactivity and Nuclear Energy. Chapter 19. http://www.youtube.com/watch?v=PEHcHcneFFc&feature=related. Chemical vs. Nuclear. Chemical Reactions. Nuclear Reactions. Involve nuclei changes Can involve e-, p+, and n o Convert 1 element to another element LARGE energy changes.

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Radioactivity and Nuclear Energy

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  1. Radioactivity and Nuclear Energy Chapter 19 http://www.youtube.com/watch?v=PEHcHcneFFc&feature=related

  2. Chemical vs. Nuclear Chemical Reactions Nuclear Reactions Involve nuclei changes Can involve e-, p+, and no Convert 1 element to another element LARGE energy changes • Break and form bonds • Created with valence electrons • Type of elements do not change during the reaction • Small energy changes

  3. Facts about the Nucleus • The nucleus is composed ofnucleons: • Neutrons and protons

  4. Isotopes and Nuclides • Isotopes: atoms that have identical atomic numbers but different mass numbers How are they similar? How are they different?

  5. Radioactivity • Radioactivity – the result of the spontaneous decomposition of an unstable nucleus. • Includes the production of high energy particles that make the nucleus more stable.

  6. Radioactive Isotopes • 85% of the 2000 known isotopes are radioactive. • 279 of those 2000 are not radioactive • Percent abundance of isotopes is much smaller. • Not radioactive: C-12 – 99% of all C • Radioactive: C-14 < 0.1%

  7. How do we know if a nucleus is stable? • Protons and neutrons are nucleons • Held together by strong nuclear force

  8. Nuclear Stability • How can you tell if an element is stable? • Look at proton to neutron ratio (p:n) • Atomic number less than 20: • Want p:n = 1:1 • Above atomic number 20  have more neutrons than protons, which increases the ratio

  9. Where are the stable nuclei found? • Band of Stability shows where the stable nuclei can be found • Depends on the proton to neutron ratio • Location determines the type of decay for the isotope

  10. How can I become a stable nucleus? 1. Alpha Radiation • Helium nuclei are emitted from a radioactive source • Called alpha particles • Contain two protons and two neutrons • Overall positivecharge Th U He

  11. How can I become a stable nucleus? 2. Beta Radiation • Fast-moving electrons created by the break-down of a neutron in an atom • Called beta particles e- C N

  12. How can I become a stable nucleus? 3. Gamma Radiation • High-energy electromagnetic radiation given off by a radioisotope • Often given-off along with alpha or beta radiation • Have no mass or charge

  13. How can I become a stable nucleus? 4. positron emission • Positron : • has same mass as an electron but the opposite charge • Created when a proton breaks apart to create a neutron and positron Be B e+

  14. How can I become a stable nucleus? • Electron capture • Capture an inner electron and turn it into a proton • “Hand of God”

  15. Practice time • Practice WS with isotopic notation and what ratio you have for Neutron to proton and types of decay – due tomorrow!!!

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