1. Ch. 25.2 Isotopes and Half-life

2. Write the alpha and beta decay of Radon-223 Alpha: 223 86 Rn → 4 2 He + 219 84 Po Beta: 223 86 Rn → 0 -1 e + 223 87 Fr

3. Radioactivity/Radiation Is a form of energy Can penetrate solid materials Radioisotopes Is generated by elements with unstable nuclei - Radioisotopes Their nucleus breaks apart and new elements are formed (transmutation Rx)

4. Radiation

5. 25.2 Half-Life of Radioisotopes total # of isotopes in PT: 1500 radioisotopes: 260 Half-Life t 1/2 :time it takes for half of the isotope to decay and form a new element Important marker used in absolute dating of fossils and artifacts

6. Half-Life Curve

7. Absolute Fossil Dating Isotope concentration at point of death = isotope concentration in environment Ex: 10g of all Carbon is C-14* Isotope concentration at time of excavation Ex: 2.5 g of all C is C-14* How much % C-14 decayed? 75 % How long does it take for this amount to decay? T1/2 of C-14 is 5,700 years

8. Concentration of old and new elements

9. Half-life of important Isotopes Bismuth-212 60.5 sec Sodium-24 15 hours Iodine-131 8.07 days Hydrogen-3 12.3 years Cobalt-40 605.26 years Carbon-14 5700 years Uranium-238 4.5 billion years

10. Practice A.How much % of new isotope is formed after 45 hours during Na-24 decay (t1/2=15 hrs) 87.5% B. How much old isotope is left after 45 hours? 12.5% C. How much C-14 is left after 11,400 years? 25% D. How much old isotope is left after 5 half lives? 3.125%

11. Ch. 25.3 Radiation in Your Life

12. Nuclear Fission Fission = splitting (of a nucleus) creates a chain reaction of high speed neutrons generates enormous amounts of energy

13. 2 Types of Fission uncontrolled nuclear reaction – A/H Bomb controlled nuclear reaction – nuclear power plant

14. Controlled Nuclear Fission Speed of the neutrons is lowered by graphite rods The coolant is heated that power steam turbines to generate electricity

15. Nuclear Reactor

16. +/- of Nuclear Energy -Forever storage of nuclear waste -Accidents that can lead to widespread contaminations (Three Mile Island, Chernobyl, Fukoshima) + no pollution, greenhouse gas emission (CO2) + independence from oil (political costs…) + long term, large scale, reliable energy production

17. Nuclear Fusion Fusion: combining (two small nuclei) more energy than nuclear fission Chain reaction Sun does nuclear fusion

18. Forces Within the Nucleus Electromagnetic repulsion: Protons repelling each other Nuclear forces: neutrons glue protons together “cosmic glue” Nuclear forces > electromagnetic repulsion, element is stable Nuclear forces < electromagnetic repulsion, radioisotope

19. 25.4 Radiation in your life

20. Ionizing Radiation Radiation with enough energy to knock electrons of the exposed elements and change them Formation of ions – charged atoms (#p+ and e- is not equal!!!) Particle radiation: alpha and beta particles Electromagnetic waves: UV, X-rays, gamma rays

21. Electromagnetic Spectrum

22. DNA Damage from Radiation

23. Dose vs Damage - radiation doses are measured in Sieverts

26. Nuclear Medicine Radiation treatment of cancer Injection of Iodine-131 for the detection of thyroid function

27. Research Radiolabeling of molecules, cell parts with radioisotopes H-3, S-35…. Dating of fossils

28. Fossil dating When the animal is alive it incorporates radioactive trace elements from environment Example: C-14 alongside C-13, C-12 T 1/2 = 5700 years When animal dies/fossilizes C-14 is not replaced but undergoes decay The older the fossil the more C-14 is gone