1. Chapter 22 Nuclear Chemistry

2. Sect. 22-1: The Nucleus Nucleons – collective name for protons & neutrons Nuclide – an atom Notation: either radium – 228 or 228 88 Ra

3. Mass Defect and Nuclear Stability Mass defect – difference between mass of atom and sum of mass of p +, n o, and e - Cause???  Mass was converted to energy when nucleus was formed (E=mc 2 where c=3.00 x 10 8 m/s) Nuclear binding energy – energy released when a nucleus forms

4. What is the mass defect of 32 16 S?  0.291764 amu What is the nuclear binding energy for that same nuclide?  4.36x10 -11 J

5. Binding energy per nucleon – binding energy divided by # of nucleons  Used to determine stability of nuclides Higher # = more stable

6. Nucleus and Nuclear Stability Band of stability Small, 1:1 is stable Large 1.5:1 is stable

7. Nuclides with even # of nucleons are typically more stable  Only 4 stable with odd # of p + and n o. Nuclear shell model – nucleons exist in energy levels (shells) in the nucleus Magic # - 2, 8, 20, 28, 50, 82, and 126… # of nucleons that represent completed energy levels (most stable)

8. Nuclear Reactions Nuclear reaction – reaction that affects nucleus Transmutation – change in identity due to change in # of protons

9. Sect. 22-2: Radioactive Decay Radioactive Decay – nucleus emitting radiation, particles, or both Nuclear radiation – particles/radiation that are released Radioactive nuclide – unstable nuclide that decays

10. Types of Radioactive Decay Alpha particle – 2 p + and 2 n o bound together  Same as Helium nucleus  2+ charge

11. Beta Particle – electron emitted from nucleus  Neutron breaks into proton and electron…electron is released  1- charge

12. Positron – same mass as electron, but + charge  proton converts to neutron & positron is released  38 19 K  38 18 Ar + 0 +1 β

13. Electron capture – inner orbital electron is captured by the nucleus  Combines with a proton to form neutron  106 47 Ag + 0 -1 e  106 46 Pd

14. Gamma rays (γ) – high energy, no mass waves emitted from nucleus  Usually accompanies one of the other types of emission

15. Half- life(t ½ ) – time it takes for ½ of the radioisotope to decay  Different for every radioisotope  # of t ½ = time elapsed length of one ½-life

16. Phosphorus-32 has a ½-life of 14.3 days. How many milligrams remain after 57.2 days if you start with 4.0mg of the isotope? 0.25mg

17. Decay series – multiple decays happen until a stable nuclide is reached  Parent nuclide – heaviest in the decay series  Daughter nuclides – products of the decay series

18. Artificial transmutation – bombardment of stable nuclei with charged & uncharged particles  Particle accelerator  Transuranium elements – elements past uranium in periodic table Created by artificial transmutation All are radioactive

19. Radiation penetrating power  Skin/paper usually stops alpha  beta only penetrates 1-2 cm into body; need lead or glass to stop it  Gamma goes all the way through body; need thick layers of lead or concrete Sect. 22-3: Nuclear Radiation

20. Units of radiation  Roentgen  Rem (roentgen equivalent, man) Used for discussing human exposure to radiation Sect. 22-3: Nuclear Radiation

21. Radiation Detection Film badges Geiger-Mϋller counters Scintillation counters

22. Applications of Nuclear Radiation Radioactive dating Radioactive tracers in medicine Radioactive nuclides in agriculture

23. Nuclear Waste From fission reactions in power plants, nuclear subs, and nuclear bombs Has very long half-lives Disposal is typically underground

24. Sect. 22-4: Nuclear Fission & Fusion Fission – nucleus splits apart Fusion – nuclei combine together Both release large amounts of energy, fusion more than fission

25. Chain reaction – one product starts another reaction Critical mass – minimum amount of nuclides needed to sustain a chain reaction

26. Nuclear power plants Shielding – radiation absorbing material Fuel - typically Uranium-235 Control Rods – neutron-absorbing; used to slow down/stop reaction Moderator – slows down fast neutrons Coolant - water