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

2. Chemical vs. Nuclear Chemical Reactions Break and form bonds Created with valence electrons Type of elements do not change during the reaction Small energy changes Nuclear Reactions Involve nuclei changes Can involve e-, p+, and n o Convert 1 element to another element LARGE energy changes

3. Facts about the Nucleus The nucleus is composed of nucleons: –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 positive charge U Th 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 C N e-

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 B Be e+e+

14. How can I become a stable nucleus? 5.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!!!