1. Nuclear Chemistry

2. Radioactive Decay Spontaneous breakdown of an atom’s nucleus Breakdown results in a lighter nucleus Emits electromagnetic radiation Nuclear radiation—radiation emitted from nucleus Radioactive nuclide– nucleus that goes through radioactive decay, unstable. (Ex. Uranium)

3. What is a nuclide Radioactive nuclide– nucleus that goes through radioactive decay unstable Contains a certain amount of energy Ex. Uranium

4. Types of Radioactive Decay 1) Alpha particle ( α ) Consists of 2 protons, 2 neutrons emitted during decay SO atomic # decreases by 2 and atomic mass decreases by 4 Helium nucleus ( 2 4 He )—how particle represented Can be stopped by paper, low penetrating power Equation: 84 210 Po  82 206 Pb + 2 4 He

5. Types of Radioactive Decay (cont.) 2) Beta particle ( β ) Releases beta particles (electron given off during radioactive decay) Negative charge causes deflection Can be stopped by lead or glass Increase in atomic # by 1, NO change in atomic mass Neutron converts to proton and electron Gaining proton, no lose in mass because neutron converted to proton— same mass Equation: 6 14 C  7 14 N + -1 0 β

6. Types of Radioactive Decay (cont.) 3) Gamma Rays Has the most energy, only stopped by lead, high penetrating power Releases gamma rays ( γ ) from nucleus Type of electromagnetic radiation Composed of photons, released as excited nuclei fall to lower energy level Ex. X-Rays

7. Types of Radioactive Decay (cont.) 4) Positron Emission Release of positrons positrons — Similar to electrons, have a positive charge Creates two gamma rays—when contact with electron Proton converted to neutron and positron Atomic # decreases by 1 due to losing proton, no mass # change Ex. 26 13 Al  26 12 Mg + 0 1 e

8. Example 1: Nuclear equation when an alpha particle emitted by 210 84 Po

9. Example 2:Nuclear equation when a beta particle emitted by 210 82 Pb

10. Practice: Alpha Decay 1) Be-9 2) U-238 3) Eu-154 Beta Decay 1) Th-234 2) K-43

11. Half-Life Time period required for half of a radioactive nuclide to decay. Vary depending on the nuclide, unique for each nuclide. Radioactive decay series— chain of radioactive decays Begins with radioactive nuclei and ends with nonradioactive nuclei Ex. U-238 Ex. 14 6 C has a half-life of 5715. Therefore, if we have 10g of 14 6 C, in 5715 years we will have 5g. Some sources say 5730 years (course textbook)

12. Half-Life (cont.) Random decay process Radioactive decay law— Rate of radioactive decay proportional to # of atoms present in sample

13. Half-Life Equation A E = A O * 0.5 t/t(1/2) A E = Substance amount A 0 = Initial substance amount t = time elapsed t 1/2 = half-life

16. Example 1: Plutonium-239 has a half life of 24,110 years. We have 100g of this substance. How many grams will we have after 96,440 years?

17. 1) Lawrencium has a half-life of 10 hours. We have a 5 gram sample of this element. How much of this sample did we have 25 hours ago. 2) Actinium has a half-life of approximately 22 years. We now have a sample of 35 grams. How much of this sample will we have in 60 years? 3) Write the alpha equation for 232 90 Th 4) Write the beta equation for 210 83 Bi

18. Nuclear Fission Nuclear reaction where nuclei are SPLIT Nucleus is broken down into a more stable nucleus heavy nucleus is broken into lighter fragments HUGE amount of energy is released Critical mass = minimum number of nuclei that can provide enough neutrons to maintain chain reaction, results in nuclear explosion. Nuclear reactors = controlled fission reactions. **Can induce a nuclear chain reaction!!!

19. Fission (cont.) Thermal neutrons bombard U-235 Mass is converted to energy 8 x 10 7 kJ/g More energy than burning coal Energy can be utilized ! First reaction causes the splitting of 2 more U-235 nuclei—generates a chain reaction

21. Nuclear Reactors Location where controlled fission reactions occur Fuel rods in the core contain enriched uranium Steam generation steam turbine electric generator Control rods take in neutrons so fission is controlled Production of radioactive waste A TON of water is used to cool the reactors

23. Nuclear Fusion Nuclei having a light mass are joined. Combination of light nuclei Creates heavy nucleus Results in larger, stable nucleus. MORE energy released than in nuclear fission !!! Hard to control Initiated by fission reaction (fission bomb) ---- H bomb **Type of reaction happening in the sun and stars. -fuel: hydrogen atom

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26. Applications Diagnostic 1) Radioisotopes Actual substance or modified into biological substance for organ targets Ex. Technetium 2) Ionizing radiation Both cancer causing and cancer treatment Use of gamma rays to target tissue Ex. Co-60 Ingestion of Radioactive Chemical Migrates to target tissue Ex. Iodine for thyroid

27. Applications (cont.) Radiation processing Used with medical supplies and food Treated with ionized radiation Kills microorganisms Radioactive Tracers Attach or “tag” to other substances Enables monitoring substance process or substance detection