1. Nuclear Chemistry Unstable Nuclei and Radioactive Decay

2. Chemical and Nuclear Reactions Chemical reactions Nuclear reactions 1. Bonds are broken and formed on the e- level. p+ and n 0 remain the same 1. Nuclei emit particles and/or rays 2. Atoms are unchanged, but can be rearranged 2. Atoms are converted into atoms of other elements by releasing energy 3. Involve valence electrons only 3. Can involve protons, neutrons, and electrons 4. Small energy changes 4. Large energy changes – huge amounts of energy released 5. Rxn rate influenced by temperature, pressure, concentration, and catalysts 5. Rxn rate not normally affected by temperature, pressure, concentration, or catalysts

3. Radioactivity Chemical reaction involves only an atom’s electrons – the nucleus remains unchanged Chemical reaction involves only an atom’s electrons – the nucleus remains unchanged Nuclear reaction involves a change in an atom’s nucleus (p+ or n 0 number) Nuclear reaction involves a change in an atom’s nucleus (p+ or n 0 number) Radioactivity is when substances spontaneously emit radiation Radioactivity is when substances spontaneously emit radiation The rays and particles emitted are radiation The rays and particles emitted are radiation

4. Radioactivity Radioactive atoms emit radiation because their nuclei are unstable (gain stability by losing energy) Radioactive atoms emit radiation because their nuclei are unstable (gain stability by losing energy) Radioactive decay is when atoms lose energy by emitting radiation in a spontaneous process. Atoms keep decaying until they form stable, nonradioactive atoms. Radioactive decay is when atoms lose energy by emitting radiation in a spontaneous process. Atoms keep decaying until they form stable, nonradioactive atoms.

5. Types of Radiation Alpha, beta, and gamma radiation have different amounts of electrical charge and are affected differently by an electric field Alpha, beta, and gamma radiation have different amounts of electrical charge and are affected differently by an electric field Radioactive source, two plates (+,-), stream of alpha, beta, and gamma rays Radioactive source, two plates (+,-), stream of alpha, beta, and gamma rays

6. Alpha Radiation 2p + and 2n 0 2p + and 2n 0 Particles deflected to (-) plate Particles deflected to (-) plate Extra protons form new element Extra protons form new element Nuclear equation: Nuclear equation: 226 88 Ra → 222 86 Rn + 4 2 He 226 88 Ra → 222 86 Rn + 4 2 He radium-226radon-222 alpha particle

8. Beta Radiation Fast moving e- Fast moving e- -1 charge -1 charge Particles deflected to (+) plate Particles deflected to (+) plate Nuclear equation: Nuclear equation: 14 6 C → 14 7 N + 0 -1 β 14 6 C → 14 7 N + 0 -1 β carbon-14 nitrogen-14 beta particle carbon-14 nitrogen-14 beta particle

10. Gamma Radiation High energy radiation without mass or electrical charge High energy radiation without mass or electrical charge Particles are not deflected by electric or magnetic fields Particles are not deflected by electric or magnetic fields Unable to form a new atom by themselves since they are mass-less Unable to form a new atom by themselves since they are mass-less They accompany other types of radiation in reactions They accompany other types of radiation in reactions 238 92 U → 234 90 Th + 4 2 He + 2 0 0 γ 238 92 U → 234 90 Th + 4 2 He + 2 0 0 γ Uranium-238 thorium-234 alpha particle gamma rays

12. Characteristics of Radiation Radiation type Symbol Mass (amu) Charge Alpha 4 2 He 42+ Beta 0 -1 β 1/18401- Gamma 00γ00γ00γ00γ00

13. Penetrating Power

14. Human Body

15. Nuclear Stability Elements > atomic number 83 are naturally radioactive Elements > atomic number 83 are naturally radioactive Ratio of p + to n 0 determines the stability of an atom Ratio of p + to n 0 determines the stability of an atom Atoms with too many or too few neutrons are unstable Atoms with too many or too few neutrons are unstable Ratio of 1.5 : 1 Ratio of 1.5 : 1

16. Fusion Reactions Nuclear process in which two light nuclei combine to form a single heavier nucleus. Examples: thermonuclear weapons and in future nuclear reactors Nuclear process in which two light nuclei combine to form a single heavier nucleus. Examples: thermonuclear weapons and in future nuclear reactors

17. Fusion Reactions The sum of the masses of the product nuclei is less than the sum of the masses of the initial fusing nuclei. The sum of the masses of the product nuclei is less than the sum of the masses of the initial fusing nuclei. E=mc 2, explains that the mass that is lost it converted into energy carried away by the fusion products. E=mc 2, explains that the mass that is lost it converted into energy carried away by the fusion products.

18. Fusion and our Universe Hydrogen isotopes collide in a star and fuse forming a helium nucleus Hydrogen isotopes collide in a star and fuse forming a helium nucleus Lighter elements fuse and form heavier elements. These reactions continue until the nuclei reach iron, the nucleus with the most binding energy. No more fusion occurs in a star because it is energetically unfavorable to produce higher masses. Once a star has converted a large fraction of its core's mass to iron, it has almost reached the end of its life. Lighter elements fuse and form heavier elements. These reactions continue until the nuclei reach iron, the nucleus with the most binding energy. No more fusion occurs in a star because it is energetically unfavorable to produce higher masses. Once a star has converted a large fraction of its core's mass to iron, it has almost reached the end of its life.

19. Fission Reactions Fission is a nuclear process in which a heavy nucleus splits into two smaller nuclei. An example of a fission reaction that was used in the first atomic bomb and is still used in nuclear reactors is: Fission is a nuclear process in which a heavy nucleus splits into two smaller nuclei. An example of a fission reaction that was used in the first atomic bomb and is still used in nuclear reactors is: 235 U + n ----> 134 Xe + 100 Sr + 2n

20. Fission Reactions Fission reactions can produce any combination of lighter nuclei so long as the number of protons and neutrons in the products sum up to those in the initial fissioning nucleus. As with fusion, a great amount of energy can be released in fission because for heavy nuclei, the summed masses of the lighter product nuclei is less than the mass of the fissioning nucleus Fission reactions can produce any combination of lighter nuclei so long as the number of protons and neutrons in the products sum up to those in the initial fissioning nucleus. As with fusion, a great amount of energy can be released in fission because for heavy nuclei, the summed masses of the lighter product nuclei is less than the mass of the fissioning nucleus

21. Fission Fission is a process that has been occurring in the universe for billions of years. We have not only used fission to produce energy for nuclear bombs, but we also use fission peacefully everyday to produce energy in nuclear power plants Fission is a process that has been occurring in the universe for billions of years. We have not only used fission to produce energy for nuclear bombs, but we also use fission peacefully everyday to produce energy in nuclear power plants

22. Fission Nuclear energy is the most certain future fuel source that we have. Currently in the U.S. 107 nuclear reactors are producing about 17% of our energy requirements. The U.S. Currently has plans of building 42 more nuclear power plants in the next 20 years. Nuclear energy is the most certain future fuel source that we have. Currently in the U.S. 107 nuclear reactors are producing about 17% of our energy requirements. The U.S. Currently has plans of building 42 more nuclear power plants in the next 20 years.

23. Downfalls to using Fission and Fusion as fuel sources… Radioactive and toxic wastes Radioactive and toxic wastes Fear/anxiety of terrorist bombing Fear/anxiety of terrorist bombing Safe storage of toxic wastes? Safe storage of toxic wastes? Construction costs more than the energy it provides Construction costs more than the energy it provides Coal still used and causing environmental issues Coal still used and causing environmental issues Can cause health problems in humans Can cause health problems in humans

24. Practical Applications of Nuclear Power Cheap Cheap Efficient Efficient Lower air pollution Lower air pollution Lower the price of electricity Lower the price of electricity Uranium is abundant on earth Uranium is abundant on earth

25. Half Life The time it takes for one-half of a radioisotope’s nuclei to decay into its products The time it takes for one-half of a radioisotope’s nuclei to decay into its products The half-life of strontium-90 is 29 years The half-life of strontium-90 is 29 years Number of half- lives Elapsed time Amount present 00 10 g 1 29 yrs 10 x (1/2)= 5 2 58 yrs 10 x (1/2)(1/2)=2.5 3 87 yrs 10 X (1/2)(1/2)(1/2)= 1.25 4 116 yrs 10x(1/2)(1/2)(1/2)(1/2)=.625

26. Half Life Amount remaining = (initial amount)(1/2) n n = the number of half-lives that have passed

27. Radioactive Decay Practice Practice Problem #1: If Gallium-68 has a half-live of 68.3 minutes, how much of a 10.0 mg sample is left after one half-life? Two half-lives? Three half-lives?

28. Radioactive Decay Practice Practice Problem #2: If the passing of five half-lives leaves 25.0 mg of a strontium-90 sample, how much was present in the beginning?