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2. Resources Bellringers Chapter Presentation Transparencies Standardized Test Prep Visual Concepts Math Skills

3. Nuclear Changes Chapter 9 Table of Contents Section 1 What Is Radioactivity? Section 2 Nuclear Fission and Fusion Section 3 Nuclear Radiation Today

4. Section 1 What Is Radioactivity? Chapter 9 Objectives • Identifyfour types of nuclear radiation and their properties. • Balanceequations for nuclear decay. • Calculatethe half-life of a radioactive isotope.

5. Section 1 What Is Radioactivity? Chapter 9 Bellringer Before studying about nuclear chemistry, answer the following items to refresh your memory about the structure of the nucleus. 1. Label the diagram shown below.

6. Section 1 What Is Radioactivity? Chapter 9 Bellringer, continued 2. Complete the table to indicate how many protons and neutrons are in the nuclei of the following atoms:

7. Section 1 What Is Radioactivity? Chapter 9 Nuclear Radiation • The process by which an unstable nucleus emits one or more particles or energy in the form of electromagnetic radiation is calledradioactivity. • The particles that are released from the nucleus during radioactive decay is callednuclear radiation. • There are different types of nuclear radiation.

8. Section 1 What Is Radioactivity? Chapter 9 Types of Nuclear Radiation

9. Section 1 What Is Radioactivity? Chapter 9 Comparing Alpha, Beta, and Gamma Particles Click below to watch the Visual Concept. Visual Concept

10. Section 1 What Is Radioactivity? Chapter 9 Nuclear Radiation, continued • Alpha particles consist of protons and neutrons. • Analpha particleis a positively charged atom that is released in the disintegration of radioactive elements and that consists of two protons and two neutrons. • Beta particles are electrons produced from neutron decay. • A beta particleis a charged electron emitted during certain types of radioactive decay, such as beta decay.

11. Section 1 What Is Radioactivity? Chapter 9 Nuclear Radiation, continued • Gamma rays are very high energy. • Agamma rayis a high-energy photon emitted by a nucleus during fission and radioactive decay. • Neutron radioactivity may occur in unstable nucleus. • Neutron emissionconsists of matter that is emitted from an unstable nucleus. • Neutrons are able to travel farther through matter than either alpha or beta particles.

12. Section 1 What Is Radioactivity? Chapter 9 Nuclear Decay • In nuclear decay, the sums of the mass numbers and the atomic numbers of the decay products equal the mass number and atomic number of the decaying nucleus. • A nucleus gives up two protons and two neutrons during alpha decay. • The process of the alpha decay of radium-226 is written as follows.

13. Section 1 What Is Radioactivity? Chapter 9 Nuclear Decay, continued • A nucleus gains a proton and loses a neutron during beta decay. • A beta decay process occurs when carbon-14 decays to nitrogen-14 by emitting a beta particle.

14. Section 1 What Is Radioactivity? Chapter 9 Alpha, Beta, and Gamma Radiation Click below to watch the Visual Concept. Visual Concept

15. Section 1 What Is Radioactivity? Chapter 9 Math Skills Nuclear DecayActinium-217 decays by releasing an alpha particle. Write the equation for this decay process, and determine what element is formed. 1. Write down the equation with the original element on the left side and the products on the right side. Use the letter X to denote the unknown product. Note that the mass and atomic numbers of the unknown isotope are represented by the letters A and Z.

16. Section 1 What Is Radioactivity? Chapter 9 Math Skills, continued 2. Write math equations for the atomic and mass numbers. 217 = A – 4 89 = Z – 2 3. Rearrange the equations. A = 217 – 4 Z = 89 – 2 4. Solve for the unknown values, and rewrite the equation with all nuclei represented. A = 213 Z = 87 The unknown decay product has an atomic number of 87, which is francium, according to the periodic table. The element is therefore

17. Section 1 What Is Radioactivity? Chapter 9 Radioactive Decay Rates • Thehalf-lifeis the time required for half of a sample of a radioactive substance to disintegrate by radioactive decay or by natural processes. • Half-life is a measure of how quickly a substance decays. • Using half-lives, scientist can predict how old an object is. • Carbon-14 is used to date materials.

18. Section 1 What Is Radioactivity? Chapter 9 Half-Life

19. Section 1 What Is Radioactivity? Chapter 9 Half-Life Click below to watch the Visual Concept. Visual Concept

20. Section 1 What Is Radioactivity? Chapter 9 Math Skills Half-lifeRadium-226 has a half-life of 1599 years. How long would it take seven-eighths of a radium-226 sample to decay? 1. List the given and unknown values. Given: half-life = 1599 years fraction of sample decayed = 7/8 Unknown: fraction of sample remaining = ? total time of decay = ?

21. Section 1 What Is Radioactivity? Chapter 9 Math Skills, continued 2. Calculate the fraction of radioactive sample remaining. To find the fraction of sample remaining, subtract the fraction that has decayed from 1. 3. Calculate the number of half-lives.

22. Section 1 What Is Radioactivity? Chapter 9 Math Skills, continued 3. Calculate the number of half-lives (continued). Three half-lives are needed for one-eighth of the sample to remain undecayed. 4. Calculate the total time required for the radio-active decay. Each half-life lasts 1599 years.

23. Section 2 Nuclear Fission and Fusion Chapter 9 Objectives • Describehow the strong nuclear force affects the composition of a nucleus. • Distinguishbetween fission and fusion, and provide examples of each. • Recognizethe equivalence of mass and energy, and why small losses in mass release large amounts of energy. • Explainwhat a chain reaction is, how one is initiated, and how it can be controlled.

24. Section 2 Nuclear Fission and Fusion Chapter 9 Bellringer In your study of chemical reactions, you learned that one convenient way to classify reactions was as synthesis or decomposition. In synthesis reactions, the products are larger and more complex than the reactants. In decomposition reactions, the opposite is true. In some situations, nuclear reactions can occur. These reactions can also be categorized by how the product nuclei compare to the reactant nuclei. Study the models of the nuclei shown below and answer the following items:

25. Section 2 Nuclear Fission and Fusion Chapter 9 Bellringer, continued

26. Section 2 Nuclear Fission and Fusion Chapter 9 Bellringer, continued 1. In which of the diagrams did a complex nucleus form simpler nuclei? 2. In which of the diagrams did simple nuclei combine to form a complex nucleus? 3. Each year, scientists around the world attempt to “discover” new elements using nuclear reactions. Which of the reactions shown in the diagrams above would be most likely to be useful for this type of research? Explain your answer.

27. Section 2 Nuclear Fission and Fusion Chapter 9 Nuclear Forces • Nuclei are held together by a special force. • Protons and neutrons are tightly packed in the tiny nucleus of an atom. • Thestrong nuclear forcecauses protons and neutrons in the nucleus to attract each other. This attraction is much stronger than the electric repulsion between protons. • Neutrons contribute to nuclear stability. • Too many neutrons or protons can cause a nucleus to become unstable and decay.

28. Section 2 Nuclear Fission and Fusion Chapter 9 Forces in the Nucleus

29. Section 2 Nuclear Fission and Fusion Chapter 9 Nuclear Fission • Fission is the process by which a nucleus splits into two or more fragments and releases neutrons and energy. • One type of fission of uranium-235 can be repre-sented by the following equation.

30. Section 2 Nuclear Fission and Fusion Chapter 9 Nuclear Fission Click below to watch the Visual Concept. Visual Concept

31. Section 2 Nuclear Fission and Fusion Chapter 9 Nuclear Fission, continued • Energy is released during a nuclear fission. • The equivalence of mass and energy observed in nature is explained by the special theory of relativity. • This equivalence is expressed by the following equation. • Mass-Energy Equation

32. Section 2 Nuclear Fission and Fusion Chapter 9 Nuclear Fission, continued • Neutrons released by fission can start a chain reaction. • Anuclear chain reaction is a continuous series of nuclear fission reactions. • Chain reactions can be controlled. • If there is less than acritical massof a fissionable isotope, a chain reaction will not occur. • Thecritical massis the minimum mass of a fissionable isotope that provides the number of neutrons needed to sustain a chain reaction.

33. Section 2 Nuclear Fission and Fusion Chapter 9 Chain Reaction

34. Section 2 Nuclear Fission and Fusion Chapter 9 Nuclear Chain Reaction Click below to watch the Visual Concept. Visual Concept

35. Section 2 Nuclear Fission and Fusion Chapter 9 Critical Mass Click below to watch the Visual Concept. Visual Concept

36. Section 2 Nuclear Fission and Fusion Chapter 9 Nuclear Fusion • Nuclear fusionis the process in which light nuclei combine at extremely high temperature, forming heavier nuclei and releasing energy. • Nuclear fusion occurs in the sun. • Four hydrogen atoms fuse together in a multi-step process to produce a helium atoms and enormous energy in the form of gamma rays.

37. Section 2 Nuclear Fission and Fusion Chapter 9 Nuclear Fusion Click below to watch the Visual Concept. Visual Concept

38. Section 3 Nuclear Radiation Today Chapter 9 Objectives • Describesources of nuclear radiation, including where it exists as background radiation. • Listand explain three beneficial uses and three possible risks of nuclear radiation. • Compareand contrast the advantages and disadvantages of nuclear energy as a power source.

39. Section 3 Nuclear Radiation Today Chapter 9 Bellringer Using what you know about radiation and nuclear reactions, answer the items below. 1. Along with a change in the nuclei involved, what other significant change occurs with radiation and nuclear reactions? 2. Radioactive isotopes are sometimes used for tracer studies, which analyze how and where a person’s body takes up a certain element. As the isotope is taken up by the body, the isotope decays, and the radiation it produces can be detected in order to determine where the element is. Based on how deep the different forms of radiation penetrate, do you think that alpha, beta, or gamma radiation is used?

40. Section 3 Nuclear Radiation Today Chapter 9 Bellringer, continued 3. In Rutherford’s famous gold-foil experiment, the patterns of deflection of the radiation that he shot at the gold foil led him to believe that the atom must contain a small, positively charged nucleus. Explain why Rutherford used alpha radiation rather than gamma radiation.

41. Section 3 Nuclear Radiation Today Chapter 9 Where is Radiation? • Nuclear radiation is all around you. Background radiation is the nuclear radiation that arises naturally from cosmic rays and from radioactive isotopes in the soil and air. • Radiation is measured in units of rems. • Aremis the quantity of ionizing radiation that does as much damage to human tissue as 1 roentgen of high-voltage X rays does.

42. Section 3 Nuclear Radiation Today Chapter 9 Where is Radiation?, continued • Exposure varies from one location to another. • Some activities add to the amount of nuclear radiation exposure.

43. Section 3 Nuclear Radiation Today Chapter 9 Beneficial Uses of Nuclear Radiation • Smoke detectors help to save lives. • In a smoke alarm, a small alpha-emitting isotope detects smoke particles in the air. • Nuclear radiation is used to detect diseases. • A radioactive tracer is a radioactive material that is added to a substance so that its distribution can be detected later. • Radioactive tracers are widely used in medicine.

44. Section 3 Nuclear Radiation Today Chapter 9 Radioactive Tracer Click below to watch the Visual Concept. Visual Concept

45. Section 3 Nuclear Radiation Today Chapter 9 Beneficial Uses of Nuclear Radiation, continued • Nuclear radiation therapy is used to treat cancer. • Radiotherapyis treatment that uses controlled doses of nuclear radiation for treating diseases such as cancer. • Agriculture uses radioactive tracers and radio-isotopes. • On research farms, radioactive tracers help scientists to understand biochemical processes in plants.

46. Section 3 Nuclear Radiation Today Chapter 9 MRI Image of a Healthy Brain

47. Section 3 Nuclear Radiation Today Chapter 9 MRI Image of Brain with Alzheimer’s

48. Section 3 Nuclear Radiation Today Chapter 9 Possible Risks of Nuclear Radiation • Nuclear radiation can ionize atoms. • Ionizationis a change in the number of electrons in an atom or molecule, causing the particle to be positively or negatively charged. • Radiation sickness results from high levels of nuclear radiation. • People working in radioactive areas wear adosimeter,a device that measures the amount of nuclear radiation exposure. • Studies have shown a relationship between exposure to high levels of nuclear radiation and cancer.

49. Section 3 Nuclear Radiation Today Chapter 9 Possible Risks of Nuclear Radiation • The risk depends upon the amount of radiation exposure. • High concentrations of radon gas can be hazardous. • Radon gasis colorless and odorless, and is produced by the decay of uranium-238 present naturally in soil and rock. • Tests for radon gas are widely available

50. Section 3 Nuclear Radiation Today Chapter 9 Nuclear Power • Nuclear fission has both advantages and disadvantages. • Nuclear fission is an alternative to fossil fuels as a source of energy. • Radioactive products of fission must be handled carefully and nuclear waste must be safely stored. • Nuclear fusion reactors are being tested. • Nuclear fusion reactions are difficult to produce in the laboratory. • Nuclear fusion also has advantages and disadvantages.