1. 1 © 2006 Brooks/Cole - Thomson Review Session: –Tuesday C-106 6-8pm

2. 2 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 23 Nuclear Chemistry © 2006 Brooks/Cole Thomson Lectures written by John Kotz

3. 3 © 2006 Brooks/Cole - Thomson Isotopes Atoms of the same element (same Z) but different mass number (A).Atoms of the same element (same Z) but different mass number (A). Boron-10 ( 10 B) has 5 p and 5 n: 10 5 BBoron-10 ( 10 B) has 5 p and 5 n: 10 5 B Boron-11 ( 11 B) has 5 p and 6 n: 11 5 BBoron-11 ( 11 B) has 5 p and 6 n: 11 5 B 10 B 11 B

4. 4 © 2006 Brooks/Cole - Thomson Radioactivity One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of Marie Curie (1876-1934).One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of Marie Curie (1876-1934). She discovered radioactivity, the spontaneous disintegration of some elements into smaller pieces.She discovered radioactivity, the spontaneous disintegration of some elements into smaller pieces.

5. 5 © 2006 Brooks/Cole - Thomson Types of Radiation

6. 6 © 2006 Brooks/Cole - Thomson Penetrating Ability

7. 7 © 2006 Brooks/Cole - Thomson Nuclear Reactions Alpha emissionAlpha emission Note that mass number (A) goes down by 4 and atomic number (Z) goes down by 2. Nucleons are rearranged but conserved Both A and Z must be balanced in nuclear reactions.

8. 8 © 2006 Brooks/Cole - Thomson Nuclear Reactions Beta emissionBeta emission Note that mass number (A) is unchanged and atomic number (Z) goes up by 1. How does this happen? Note that both A and Z are balanced.

9. 9 © 2006 Brooks/Cole - Thomson Nuclear Reactions Gamma rays – very high energy waves!Gamma rays – very high energy waves!  -rays are sometimes produced after  or  emissions. Radioactive decay generates a new nucleus, but possibly in an unstable configuration of p +, n. E Nuclear energy levels A drop in energy level emits a  -ray.

10. 10 © 2006 Brooks/Cole - Thomson Origin of the Elements The Big Bang Theory The Big Bang Theory In the first moments there were only 2 elements — hydrogen and helium In the first moments there were only 2 elements — hydrogen and helium

11. 11 © 2006 Brooks/Cole - Thomson Element Abundance

12. 12 © 2006 Brooks/Cole - Thomson Stability of Nuclei Screens 23.3 and 23.4 H is most abundant element in the universe.H is most abundant element in the universe. –88.6% of all atoms –He is 11.3% of all atoms – H + He = 99.9% of all atom & 99% of mass of the universe. This tells us about the origin of the elements, and so does the existence of isotopes.This tells us about the origin of the elements, and so does the existence of isotopes.

13. 13 © 2006 Brooks/Cole - Thomson Half-Life Section 15.4 & Screen 23.6 HALF-LIFE is the time it takes for 1/2 a sample is disappear.HALF-LIFE is the time it takes for 1/2 a sample is disappear. The rate of a nuclear transformation depends only on the “reactant” concentration.The rate of a nuclear transformation depends only on the “reactant” concentration. Concept of HALF-LIFE is especially useful for 1st order reactions.Concept of HALF-LIFE is especially useful for 1st order reactions.

14. 14 © 2006 Brooks/Cole - Thomson Half-Life Decay of 20.0 mg of 15 O. What remains after 3 half-lives? After 5 half-lives?

15. 15 © 2006 Brooks/Cole - Thomson Kinetics of Radioactive Decay Activity (A) = Disintegrations/time = (k)(N) where N is the number of atoms Decay is first order, and so ln (A/A o ) = -kt The half-life of radioactive decay is t 1/2 = 0.693/k

16. 16 © 2006 Brooks/Cole - Thomson Nuclear Fission http://chemincontext.eppg.com/chapter7/FiguresAlive.html April 26 th, 1986 – Chernobyl Disaster

17. 17 © 2006 Brooks/Cole - Thomson Nuclear Fission & Lise Meitner 109 Mt

18. 18 © 2006 Brooks/Cole - Thomson Nuclear Fission & POWER Currently about 103 nuclear power plants in the U.S. and about 435 worldwide.Currently about 103 nuclear power plants in the U.S. and about 435 worldwide. 17% of the world’s energy comes from nuclear.17% of the world’s energy comes from nuclear.

19. 19 © 2006 Brooks/Cole - Thomson Image from: http://www.animatedsoftware.com/hotwords/nuclear_reactor/nuclear_reactor.htm

20. 20 © 2006 Brooks/Cole - Thomson Radon – a deadly gas? More  t 1/2 = 3hr t 1/2 = 3d + + + Rn atoms settle in lungs and eject an  particle.

21. 21 © 2006 Brooks/Cole - Thomson Units for Measuring Radiation Curie: 1 Ci = 3.7 x 10 10 distintegrations/s SI unit is the becquerel: 1 Bq = 1 dps Rad: measures amount of energy absorbed 1 rad = 0.01 J absorbed/kg tissue Rem: based on rad and type of radiation. Quantifies biological tissue damage Usually use “millirem”

22. 22 © 2006 Brooks/Cole - Thomson Effects of Radiation

23. 23 © 2006 Brooks/Cole - Thomson

24. 24 © 2006 Brooks/Cole - Thomson Nuclear Medicine: Imaging

25. 25 © 2006 Brooks/Cole - Thomson Nuclear Medicine: Imaging Technetium-99m is used in more than 85% of the diagnostic scans done in hospitals each year. Synthesized on-site from Mo-99. 99 42 Mo ---> 99m 43 Tc + 0 -1  99m 43 Tc decays to 99 43 Tc giving off  ray. Tc-99m contributes in sites of high activity.

26. 26 © 2006 Brooks/Cole - Thomson Nuclear Medicine: Imaging Imaging of a heart using Tc-99m before and after exercise.

27. 27 © 2006 Brooks/Cole - Thomson Food Irradiation Food can be irradiated with  rays from 60 Co or 137 Cs.Food can be irradiated with  rays from 60 Co or 137 Cs. Irradiated milk has a shelf life of 3 mo. without refrigeration.Irradiated milk has a shelf life of 3 mo. without refrigeration. USDA has approved irradiation of meats and eggs.USDA has approved irradiation of meats and eggs.