1. NUCLEAR CHEMISTRY

2. Atomic Structure Recall: Atoms – consist of a positively charged nucleus, which has protons and neutrons. IsotopeSymbol# protons# neutronsAtomic Mass Mo-101 H-2 C-14 U-238 Bi-210 He-4 42 1 6 92 83 2 59 1 8 146 127 2 101 2 14 238 210 4 Isotope – atoms of the same chemical element that have a different number of neutrons. Each isotope of a given element is designated by the total number of its protons plus its neutrons.

3. Difference between the mass of an atom and the mass of its individual particles. 4.00260 amu4.03298 amu Mass Defect Nuclear Forces

4. Nuclear Binding Energy Energy released when a nucleus is formed from nucleons. High binding energy = stable nucleus. E = mc 2 E:energy (J) m:mass defect (kg) c:speed of light (3.00×10 8 m/s)

5. Nuclear Binding Energy Unstable nuclides are radioactive and undergo radioactive decay. The seven most widely recognized magic numbers as of 2007 are 2, 8, 20, 28, 50, 82, 126

6. Types of Radiation Alpha particle (  ) –helium nucleus paper 2+ Beta particle (  -) –electron 1- lead Positron (  +) –positron 1+ Gamma (  ) –high-energy photon 0 concrete ChargeShielding

8. Penetrating Ability of Radiation

9. Nuclear Decay Transmutation- One element becomes another. More than 83 protons means that the nuclei is unstable (radioactive)

11. Alpha Emission parent nuclide daughter nuclide alpha particle Numbers must balance!! occurs when the nucleus has too many protons which cause excessive repulsion.

12. Beta Emission electron occurs when the neutron to proton ratio is too great.

13. Neutron to Proton

14. Ex. Polonium-210 undergoes beta decay to produce this daughter nuclide + Beta Emission =

15. positron Positron Emission Occurs when the neutron to proton ratio is too small.

16. Ex. Polonium-210 undergoes positron emission to produce this daughter nuclide + Positron Emission =

17. Electron Capture electron occurs when the neutron to proton ratio in the nucleus is too small.

18. Ex. Polonium-210 captures an electron to produce this daughter nuclide + Electron Capture =

19. Gamma Emission –Emission of high energy electromagnetic wave. occurs when the nucleus is at too high an energy.

20. Ex. Polonium-210 undergoes gamma decay to produce this daughter nuclide + Gamma Emission =

21. Types of Radiation

22. Nuclear Fission – splitting of heavier nuclei into lighter nuclei. energy + + 15 + + How much energy? E=mc 2 _______= _______ x (_____ _ _____) 2 c=3.0x10 8 Energymassspeed of light E=mc 2 explains _____ _____ (total mass of nucleus is less than sum of individual particles) mass defect

24. Nuclear Fusion - Energy released when two light nuclei combine or fuse However, a large amount of energy is required to start a fusion reaction: o Need this energy to overcome ________ forces of protons. o Extremely high temperatures can provide start-up energy. repulsion More energy in fusing hydrogen that fission of uranium

25. Nuclear Fusion

26. A Decay Series A radioactive nucleus reaches a stable state by a series of steps

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28. Half-life Concept

29. Decay Kinetics Decay occurs by first order kinetics (the rate of decay is proportional to the number of nuclides present) N = number of nuclides remaining at time t N 0 = number of nuclides present initially k = rate constant t = elapsed time

30. Calculating Half-life t 1/2 = Half-life (units dependent on rate constant, k )

31. Sample Half-Lives

32. Half-life m f :final mass m i :initial mass n:# of half- lives