Nuclear Chemistry

1. Nuclear Chemistry CHAPTER 10 Intro Clip (2:40)

2. 10.1 Radioactivity • Radioactivity - when an unstable atomic nucleus emits charged particles and energy. • Nuclear decay - atoms of 1 element can change into atoms of a different element.

3. Over100 mammoths died at a sinkhole in Hot Springs, South Dakota. • Can you determine a way to calculate how old these once furry elephants might be?

4. Carbon-14 Dating They are about 26,000 years old. Mammoth Tooth FYI: Ms. Lolich went here on a quick trip west. Yes…….she is a science geek.

5. Nuclear radiation • Charged particles & energy that are emitted from the nuclei of radioisotopes. • Alpha • Beta • Gamma

6. Alpha Decay • positively charged (+2) • 2 protons and 2 neutrons (like He but no e) • symbol 42He or the Greek letter α. • Low penetrating power • Travel only a few cm. thru air. • Does not pose a health hazard

7. What do those numbers mean? Mass Number Atomic Number

8. Example of Alpha Decay 24094 Pu 23692 U + 42 He

9. Ask Ms. Lolich for her Weird way to remember this……

10. Beta Decay • Occurs when a neutron decomposes into a proton and an electron. • negative charge • no mass • symbol 0−1e or the Greek letter β. • 100x more penetrating than the α particle. • Can pass through clothing and damage skin. • * assigned an atomic number of −1

11. Example of Beta Decay 22888 Ra 22889 Ac + 0-1e

12. B “e”TA DECAY Ask Ms. Lolich for her Weird way to remember this……

13. Gamma Decay • Energetic form of light similar to X-ray • Has no mass - does not affect atomic # or mass # (like an electron) • Often occurs with α and β radiation • no charge • Greek symbol is γ • Can travel through tissue and solid material - stopped by concrete and lead.

14. Example of Gamma Decay 24094 Pu 24094 Pu + γ radiation

15. Penetrating Powers of Nuclear Radiation

16. Notice the red dotted line

19. Effects of Nuclear Radiation Background radiation - naturally occurs in the environment. 1. You’re exposed daily. 2. Found in: air, water, rocks, plants, and animals, comic rays. 3. Not harmful.

20. Effects of Nuclear Radiation Once nuclear radiation exceeds background levels, it can damage the cells and tissues of your body. David Hahn needs Proactive – NOT!

21. Detecting Nuclear Radiation • Devices that are used to detect nuclear radiation include: • Geiger counters • Film badges.

22. 10.2 Rates of Nuclear Decay • A half-life is the time required for one half of a sample of a radioisotope to decay. Video Clip (1:24)

23. So how long does it take anyhow? • Half-lives can vary • fractions of a second • billions of years. • Nuclear decay rates are constant.

24. The half-life for iodine-131 is 8.07 days.

25. After one half-life (8.07 days), half of a sample of iodine-131 will have decayed into xenon-131.

26. After two half-lives (16.14 days), three quarters of the sample will have decayed.

27. After 3 half-lives (24.21 days), what % will be remaining?

28. Half-lives of various Radioisotopes

29. Lab to follow • Calculating Half-Life of BariumStudents will observe radioactive decay and collect data from their Geiger counter to graph the half-life decay process.

30. 10.3 Artificial Transmutation • Transmutation - conversion of atoms of 1 element to atoms of another. • Involves a nuclear change, NOT a chemical change. Video Clip (2:04)

31. Who’s your daddy daughter?

32. Natural all the way • In natural transmutations, the nucleus decays spontaneously. • There is only 1 reactant (or the nucleus) that undergoes the transformation. • Alpha or beta particles are emitted.

33. So how do they do it artificially? • Scientists bombard the atomic nuclei with high-energy particles such as protons, neutrons, or alpha particles. • Particles are accelerated in accelerators, by using electric and magnetic fields.

34. Way to go Ernie!! • In 1919, Ernest Rutherford bombarded nitrogen-14 with α particles. • Notice the left side balanced with right.

35. You try….determine “X”? 4 He 2

36. One more time….Determine “X”? 30 P 15

37. 10.4 Fission and Fusion • P4.12d • Identify the source of energy in fission and fusion nuclear reactions. Video Clip (FIRST 1:06 )

38. So what isnuclear force? • Binds protons and neutrons together in the nucleus. • Over very short distances its greater than the electric forces. Remember + and + repel but NOT with nuclear force!!

39. Fission • The splitting of an atomic nucleus into two smaller parts. • Tremendous amounts of energy are produced from very small amounts of mass. • This is how our nuclear reactor plants work.

40. Did you know? • 1 kilogram of uranium-235 is equal to the chemical energy produced by burning more than 17,000 kilograms of coal!

41. Nuclear Fission of Uranium-235

42. Nuclear Fission of Uranium-235

43. Nuclear Fission of Uranium-235

44. Nuclear Fission of Uranium-235

45. Real live “action” shots of Fission

46. What Ms. Lolich sees in her head FISSION ISSIO SCISSORS ISSO So Fission is like Scissors – right?

47. Fusion • When the nuclei of 2 atoms combine to form a larger nucleus. • Fusion also has a small fraction of the reactant mass that is converted into energy. • This is how our sun works and reactor made in Junkyard Science article.

48. What do you need you ask? • High temperatures. • Plasma must exist. • Plasma is a state of matter in which atoms have been stripped of their electrons. Think of plasma (gas) = nuclei & electrons

49. Let’s break it down…. …More like “stick it” together.

50. Something to consider as we end our chapter. Video Clip (3:26)