Understanding Radioactivity: Types, Reactions & Energy

2. Chapter Menu Section 21.1Types of Radioactivity Section 21.2 Nuclear Reactions and Energy Section 21.3 Nuclear Tools Click a hyperlink to view the corresponding slides. Chapter Menu

3. Types of Radioactivity Analyze common sources of background radiation. Compare and contrast alpha, beta, and gamma radiation. Apply the concept of half-life of a radioactive element. Section 21.1

4. Types of Radioactivity photosynthesis: the process used by certain organisms to capture energy from the Sun Section 21.1

5. Types of Radioactivity radioactivity alpha particle beta particle gamma ray half-life Alpha, beta, and gamma radiation are three types of radiation emitted as unstable nuclei decay into stable nuclei. Section 21.1

6. Discovery of Radioactivity Henri Becquerel discovered that uranium compounds spontaneously give off radiation. Section 21.1

7. Discovery of Radioactivity (cont.) Marie and Pierre Curie concluded that a nuclear reaction was taking place within the uranium atoms. Radioactivity is the spontaneous emission of radiation by an unstable atomic nucleus. Section 21.1

8. Nuclear Notation Nuclear reactions are different from other types of reactions. Section 21.1

9. Nuclear Notation (cont.) Nuclear reactions involve the protons and neutrons found in the nucleus. When writing nuclear equations, it is important to indicate the isotopes of the given elements. Section 21.1

10. Radioactive Decay Isotopes of atoms with unstable nuclei are called radioisotopes. Unstable nuclei emit radiation to attain more stable atomic configurations in a process called radioactive decay. Section 21.1

11. Radioactive Decay (cont.) There are three types of nuclear radiation: alpha, beta, and gamma. Alpha radiation consists of streams of alpha particles(α), which are helium nuclei consisting of two protons and two neutrons. Section 21.1

12. Radioactive Decay (cont.) Alpha radiation is not very penetrating—a single sheet of paper will stop an alpha particle. Section 21.1

13. A beta particle is a high-energy electron with a 1– charge and is written as Radioactive Decay (cont.) Whenever beta decay occurs, transmutation of elements occurs. Beta radiation is a stream of fast moving particles with greater penetrating power—they can only be stopped by stacked sheets of metal, blocks of wood, or heavy clothing. Section 21.1

14. Radioactive Decay (cont.) A gamma ray (γ) is a high-energy form of electromagnetic radiation without mass or charge. Gamma rays are more difficult to stop than alpha or beta particles. Section 21.1

15. Radioactive Decay (cont.) Gamma rays almost always accompany alpha and beta radiation. During gamma decay, only energy is released. Gamma radiation is often omitted from nuclear equations because it does not affect mass number or atomic number. Section 21.1

16. Radioactive Decay (cont.) Determining mode of decay • Both the atomic number and mass number decrease = alpha decay • Mass number stays the same and atomic number increases = beta decay • No change to mass number or atomic number = gamma radiation Section 21.1

17. Radioactive Decay (cont.) There are several methods used to detect radiation. • photographic film • scintillation counters • A Geiger counter detects ionizing radiation, which is radiation energetic enough to ionize matter with which it collides. Section 21.1

18. Half-Life and Radioisotope Dating The rate of spontaneous nuclear decay cannot be changed. Radioactive decay rates are measured in half-lives. The half-life is the time it takes for half of a given amount of a radioactive isotope to undergo decay. Section 21.1

19. Half-Life and Radioisotope Dating (cont.) Section 21.1

20. Half-Life and Radioisotope Dating (cont.) Four different isotopes are commonly used for dating objects: carbon-14, uranium-238, rubidium-87, and potassium-40. Carbon-14 dating is commonly used to measure the age of fossils. To date objects that are more than 60,000 years old, carbon-14 dating cannot be used since there is very little carbon left to measure. Section 21.1

21. Section Assessment Which is not a type of nuclear radiation? A.alpha B.beta C.gamma D.omega Section 21.1

22. Section Assessment Why do radioisotopes emit radiation? A.to balance charges in the nucleus B.to release energy C.to attain more stable atomic configuration D.to gain energy Section 21.1

23. End of Section 21.1

24. Nuclear Reactions and Energy Compare and contrast nuclear fission and nuclear fusion. Demonstrate equations that represent the changes that occur during radioactive decay. Trace the operation and structure of a fission reactor. Section 21.2

25. Nuclear Reactions and Energy half-life: the time it takes for half of a given radioactive isotope to decay (into a different isotope or element) Section 21.2

26. Nuclear Reactions and Energy nuclear fission nuclear reactor nuclear fusion deuterium tritium Fission and fusion release tremendous amounts of energy. Section 21.2

27. The Power of the Nucleus Nuclear reactions involve enormous energy changes. Albert Einstein was the first scientist to realize the enormous amount of potential energy available in matter and related it in the equation, E = mc2. Section 21.2

28. Nuclear Fission Nuclear fission is the splitting of an atomic nucleus into two or more smaller fragments, accompanied by a large release of energy. Section 21.2

29. Nuclear Fission (cont.) Nuclear power plants use fission to produce electricity by striking uranium-235 with neutrons. • Fission of an atom of uranium-235 releases two neutrons. • Each of those neutrons can split an atom of uranium, which releases more neutrons. • The self-sustaining process is called a chain reaction. Section 21.2

30. Nuclear Fission (cont.) Section 21.2

31. Nuclear Fission (cont.) A sample that has enough fissionable material to sustain a chain reaction has critical mass. A sample that does not have fissionable material to sustain a chain reaction has subcritical mass. Section 21.2

32. Nuclear Fission (cont.) If there is a much greater amount of material present, called supercritical mass, the chain reaction quickly escalates, an explosion occurs, and an enormous amount of energy is released at once. • Atomic bomb Section 21.2

33. Nuclear Fission (cont.) Section 21.2

34. Nuclear Fission (cont.) A nuclear reactor is a device that is used to extract energy from a radioactive fuel. Breeder reactors produce more fuel than they consume. Section 21.2

35. Nuclear Fission (cont.) Section 21.2

36. Nuclear Fission (cont.) Although nuclear reactions do not produce pollutants such as carbon dioxide and acidic sulfur and nitrogen compounds, nuclear reactors do form highly radioactive waste that is hard to dispose of safely. Section 21.2

37. Nuclear Fusion Nuclear fusion is the process of combining two or more nuclei to form a larger nucleus. The enormous amount of energy that is generated by fusion reactions in the Sun sustains all life on Earth. Section 21.2

38. Nuclear Fusion (cont.) In one common fusion reaction, two different isotopes of hydrogen combine to form helium and a neutron. Section 21.2

39. Nuclear Fusion (cont.) The isotope of hydrogen with a mass number of 2 that is one of the reactants is called deuterium (D). The hydrogen isotope with a mass number of 3 is called tritium (T). Section 21.2

40. Nuclear Fusion (cont.) Fusion has several advantages over fission. • Lightweight isotopes are abundant. • Fusion products are not radioactive. • Fusion reactions are easier to control. Section 21.2

41. Nuclear Fusion (cont.) Problems with fusion • Fusion requires extremely high energies to initiate and sustain a reaction. • Any material used to contain the reaction would melt at the temperatures necessary to trigger nuclear fusion. Section 21.2

42. Nuclear Fusion (cont.) Tokamak reactors are most promising reactor type but still need to overcome engineering issues to produce energy. Section 21.2

43. Section Assessment The hydrogen isotope which is often used in nuclear fusion reactions and has a mass number of 3is called: A.deuterium B.tritium C.alpha D.beta Section 21.2

44. Section Assessment The self-sustaining process in a nuclear fission is called a ___. A.fusion B.catalyst C.chain reaction D.half-life Section 21.2

45. End of Section 21.2

46. Nuclear Tools Distinguish the biological effects of radiation and the units used to measure levels of exposure. Illustrate medical and nonmedical uses for radioactivity. Section 21.3

47. Nuclear Tools nuclear fusion: the process in which two or more nuclei combine to form a larger nucleus Section 21.3

48. Nuclear Tools gray sievert Radiation has many useful applications, but it also has harmful biological effects. Section 21.3

49. Medical Uses of Radioisotopes When used safely, radiation can be very useful. Radioisotopes can trace and identify abnormalities in the body, and are widely used in diagnosis to generate images of organs and glands. Section 21.3

50. Nonmedical Uses of Radioisotopes If a radioisotope is substituted for a nonradioactive isotope of the same element in a chemical reaction, all compounds formed from that element in a series of steps will also be radioactive. Section 21.3