What do they have in common?

1. What do they have in common?

2. Nuclear Chemistry

3. Nuclear Reactions • Involve the nucleus • Radioactivity is the spontaneous emission of radiation from an atom

4. Nuclear Stability • Most atoms have a stable nucleus • A strong nuclear force holds protons and neutrons together • Neutrons act as the “glue” holding the protons together

5. Belt of Nuclear Stability There seems to be a ratio of protons to neutrons that increase the chances that an atom will be stable. Figure 18.1 The Zone of Stability

6. Types of Radiation • The three main types of nuclear radiation are alpha radiation, beta radiation, and gamma radiation.

7. Alpha particle - Helium nucleus with no electrons +2 charge Beta particle - High energy stream of electrons -1 charge Gamma Rays - High energy wave which are the strongest No charge Refer to the radioactive particle sheet that can be found on the website for other particles. Radioactive Particles

8. A look at Alpha Decay

9. A look at Beta Decay

10. A look at Gamma Decay

11. Penetrating Powers

12. Nuclear Equations • Scientists use a nuclear equation when describing radioactive decay • The mass number and atomic number must add up to be the same on both sides of the equation

13. Balancing Nuclear Equations • Here’s the equation from the previous slide. • The top numbers on the left side of the arrow = the top numbers on the right side of the arrow. • The same holds for the bottom numbers. • USE A PERIODIC CHART for the atomic numbers if needed.

14. Beta Decay • Beta decay results in an increase in the atomic number. • Notice how the top numbers equal and the bottom numbers also equal

15. Nuclear Stability and Decay For the equations on the right, the atomic numbers are also shown but in many equations they are omitted because they can be found on the periodic chart. For example, carbon is often written as: 14C

16. Practice • Write the nuclear equation of the alpha decay of Radon – 226 • Write the nuclear equation of the alpha decay of Gold – 185 • The number after the element is the mass number.

17. Practice Answers • 226Rn  4He + 222Po • 185Au  4He + 181Ir

18. Practice • Write the nuclear equation of the beta decay of Iodine - 131 • Write the nuclear equation of the beta decay of Sodium - 24

19. Practice Answers • 131I  -1e-1 + 131Xe • 24Na  -1e-1 + 24Mg

20. Half Life • Radioisotopes are radioactive isotopes of elements (not all isotopes are radioactive) • A half-life is the amount of time it takes for one half of a sample to decay. • The half-life is different for each element and isotope. • http://www.colorado.edu/physics/2000/isotopes/radioactive_decay3.html

21. Beta Decay of Phosphorous - 32 Notice that every 14 days, the amount is cut in half.

22. Radiocarbon Dating • Carbon - 14 undergoes beta decay to form stable nitrogen 14 • Half life of 5,730 years • Used to approximate ages 100 – 30,000 years • Other radioisotopes are used to measure longer periods of time

23. Parent and Daughter Nuclides • The term parent nuclide refers to the original atom. • The term daughter nuclide refers to the particle that is produced after the radioactive decay is completed.

24. Some examples of Parent – Daughter Nuclides

25. Practice • The half-life of Po-218 is three minutes. How much of a 2.0 gram sample remains after 15 minutes? • Remember that the symbol for half life is t1/2

26. Practice Answer • It is often best to set up a simple table especially if the amount of time is a multiple of the half life like in this example. • Notice that 15 minutes is a multiple of the 3 minute half – life. • The next slide has the table that we need to create to solve the problem.

27. Practice Answer: Half – Life Table So after 15 minutes, there is only .0625 grams left.

28. Practice • Three grams of Bismuth-218 decay to 0.375 grams in one hour. • What is the half-life of this isotope?

29. Practice Answer Half – Life Table We can also create the table going backwards to answer questions like this one. Notice it is really a similar table. It took 3 half-lives to get to the amount .375 grams. If 1 hour equals 3 half-lives, then each half-life must be 20 minutes.

30. More on Half - Life • Sometimes the amount of time is not a multiple of number of half-lives. • We can use the following equation for all half-life problems.

31. Nuclear Bombardment • Nuclear scientists change elements by bombarding the nucleus with particles – transmutation 14N + 4He  17O + 1H • Leads to the creation of transuranium (after U) elements.

32. Transmutation Reactions • The first artificial transmutation reaction involved bombarding nitrogen gas with alpha particles.

33. Fermilab Particle Accelerator

34. Nuclear Power • Nuclear Reactors use fission of Uranium-235 as source of energy • A large nucleus is split into two smaller nuclei • A small amount of mass is converted to a tremendous amount of energy (E = mc)2 • About 1 kg of Uranium-235 = 2.2 million gallons of gasoline • http://people.howstuffworks.com/nuclear-power2.htm

35. Nuclear Fission • Nuclear Fission

36. Fission Produces a Chain Reaction

37. Overview of a nuclear power plant All power plants work on the same principal. It needs to heat up water to make steam to run a steam engine which produces the actual electricity. The only difference between a coal power plant and a nuclear power plant is that the first burns coal to heat the water and the second controls a nuclear reaction to heat the water.

38. Nuclear Power Plants # 1 • A nuclear plant has some differences of course compared to a coal burning plant. • The fuel is much more costly, though lasts much longer. • The heat can be controlled easily in a coal burning plant by simply controlling how much coal is added to the fire. • This is the primary difference and the biggest safety concern in a nuclear power plant as the next slide shows.

39. Nuclear Power Plants # 2 • Uranium fuel can’t be removed or limited like a coal fired power plant. • The heat comes from the chemical reaction of the decay of a uranium atom. • The atom splits and the chain reaction keeps it going. • The way to control the heat released is by controlling the neutrons released • during the chain reaction. • This is done by using graphite rods that can be raised and lowered which controls the amount of neutrons absorbed at any time.

40. Nuclear Power Plants # 3 • This was the primary problem in developing the • atomic bomb during World War 2. • Both sides knew how to get the fission process of the uranium going, but the questions were on how to keep it under control so it wouldn’t go off too early in the lab. • There were two teams. One team was working for Germany. The other team was a group of mostly German scientists who were able to flee Germany to the United States and were working for the Allied forces.

41. Nuclear Power Plants # 4 The team working in Germany focused on using heavy water to moderate the chain reaction. Heavy water is regular water but with a difference in the hydrogen isotope. Regular water is mostly 1H but heavy water is 2H. This extra neutron helps to absorb other neutrons and control the reaction. Regular water is about .0001 % heavy water but the percentage needed is about 98 % so it took time to get enough heavy water needed.

42. Nuclear Power Plants # 5 The allied side, based in the United States decided to use graphite rods which could be raised and lowered and absorb the neutrons. While both were acceptable ways to moderate the reaction, the Allied side was able to create the bomb first and force an end to the war.

43. A Schematic Diagram of a Reactor Core

44. Gun-triggered fission bomb(Little Boy - Hiroshima)Implosion-triggered fission bomb (Fat Man - Nagasaki) http://people.howstuffworks.com/nuclear-bomb5.htm

46. Nuclear Power Plants # 6 An interesting side note to all of this is how nuclear energy in power plants came to be. The scientists who were working on the bomb were uneasy with this type of power and the US government put out a survey to ask how can this energy source by used peacefully. Some answers such as to create a new Panama Canal were tossed aside (too much residual radiation). Suggestions were that if the reaction can be controlled it can be used to run steam turbines in power plants. This led to the start of the nuclear power plant.

47. A schematic of a nuclear power plant What the heat from the radioactive process does is to heat water to run a turbine.

48. Nuclear Fusion Atomic nuclei fuse releasing a tremendous amount of energy

49. Nuclear Weapons • The bombs dropped in World War 2 were fission bombs made of Uranium and getting their energy when the Uranium atoms split (fission) into smaller atoms. This is called an Atomic Bomb. • Since then, the process of taking Hydrogen atoms and combining 4 of them to create a Helium atom (fusion) has been developed. This creates a more powerful bomb. This is called a Nuclear Bomb.

50. Radiation and You • SI units are in Curies (Ci) • One Curies is amount of nuclear disintegrations per second from one gram of radium • Also measured in rem (Roentgen Equivalent for Man) • Over 1000 rem is fatal • The next slide gives a glimpse of the radiation we receive. NOTE that the units are MILLIREMS, which is 1/ 1,000 of a REM.