25.1 NUCLEAR RADIATION Section Review Objectives Explain how an unstable nucleus releases energy Describe the three main types of nuclear radiation Vocabulary radioisotopes radioactivity radiation alpha particle beta particle gamma ray Part A Completion Use this completion exercise to check your understanding of the concepts and terms that are introduced in this section. Each blank can be completed with a term, short phrase, or number. Isotopes with unstable nuclei are 1 and are called 1. 2. The 3 of radioisotopes decay to 4 nuclei 2. plus emission of large amounts of 5. The radiation may 3. be alpha, 6, or gamma. 7 radiation consists of 4. alpha particles (positively charged 8 nuclei) that are easily 5. stopped by a sheet of paper. Beta radiation is composed of 6. fast-moving particles, which are 9. Beta radiation is more 7. penetrating than alpha radiation; it is stopped by 10. 8. 11 radiation is electromagnetic radiation. Gamma radiation 9. has no 12 or electrical charge. It is extremely penetrating. 10. 13 bricks and 14 reduce the intensity of gamma 11. radiation but do not completely 15 it. 12. 13. 14. 15. Chapter 25 Nuclear Chemistry 661
Part B True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT. 16. Beta radiation is emitted when a radioisotope decays. 17. Gamma radiation has a negative charge 18. Gamma radiation is high-energy electromagnetic radiation. 19. 238 92U 0 1 e 239 92 U 20. When a beta particle is emitted, the atomic number increases by 1, and the mass number stays the same. Part C Matching Match each description in Column B to the correct term in Column A. Column A 21. radioisotopes 22. radioactive decay 23. gamma ray Column B a. the process in which an unstable nucleus releases energy by emitting radiation b. isotopes that have unstable nuclei and undergo radioactive decay c. high-energy photon with no mass or electrical charge 24. alpha particles 25. beta particles Part D Problems Answer the following in the space provided. 26. Write nuclear equations for these processes. a. The alpha decay of 218 84 Po b. The beta decay of 210 82 Pb d. electrons resulting from the breaking apart of a neutron in an atom e. helium nuclei emitted from a radioactive source 662 Core Teaching Resources
25.2 NUCLEAR TRANSFORMATIONS Section Review Objectives Describe the type of decay a radioisotope undergoes Make calculations that involve half-life Explain the two ways transmutations can occur Vocabulary band of stability positron half-life transmutation transuranium elements Part A Completion Use this completion exercise to check your understanding of the concepts and terms that are introduced in this section. Each blank can be completed with a term, short phrase, or number. Nuclei that lie outside the 1 undergo spontaneous 1. radioactive decay. Nuclei with too many neutrons undergo 2. 2 emission as neutrons are converted to protons. A 3 3. is a particle with a positive charge and the mass of an electron. 4. Every radioisotope decays at a characteristic 4. A 5. 5 is the time required for one half of the nuclei in a radio- 6. isotope to decay. The product nuclei may or may not be 6. 7. Half-lives vary from fractions of a second to 7 of years. 8. The conversion of atoms of one element to atoms of another 9. is called 8. This process can occur by 9 or when 10. particles bombard the nucleus of an atom. All of the elements 11. with 10 above 92 have been 11 in nuclear reactors or accelerators. Chapter 25 Nuclear Chemistry 663
Part B True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT. 12. If you start with one mole of a radioisotope, after 10 half-lives, there will be none of the isotope left. 13. A radioisotope has a half-life of 12 minutes. After 36 minutes only one third of the radioactive atoms initially present will remain. 14. Transuranium elements have atomic numbers greater than 92. 15. Transmutation reactions occur spontaneously. 16. Positively charged particles have the mass of an electron. Part C Matching Match each description in Column B to the correct term in Column A. Column A Column B 17. band of stability 18. positron 19. half-life a. conversion of an atom of one element to an atom of another element b. time required for one half of the nuclei of a radioisotope to decay to products c. region containing stable nuclei in a neutron vs. proton plot 20. transmutation 21. transuranium elements Part D Questions d. elements with atomic numbers higher than 92 e. particle with the same mass as an electron but with a positive charge Answer the following in the space provided. 22. Sodium-24 has a half-life of 15 hours. How much sodium-24 will remain in an 18.0-g sample after 60 hours? 23. After 42 days, a 2.0-g sample of phosphorus-32 contains only 0.25 g of isotope. What is the half-life of phosphorus-32? 664 Core Teaching Resources
25.3 FISSION AND FUSION OF ATOMIC NUCLEI Section Review Objectives Describe what happens in a nuclear chain reaction Explain the role of water in the storage of spent fuel rods Compare and contrast fission and fusion reactions Vocabulary fission neutron moderation neutron absorption fusion Part A Completion Use this completion exercise to check your understanding of the concepts and terms that are introduced in this section. Each blank can be completed with a term, short phrase, or number. Nuclear 1 occurs when fissionable isotopes are 1. bombarded with 2. The 3 breaks into two fragments 2. of about the same size, and in the process they release more 3. neutrons and 4. 4. Neutron 5 is the process that reduces the speed of 5. neutrons. Neutron 6 is the process that decreases the 6. number of slow-moving neutrons. In nuclear 7, nuclei 7. combine to make nuclei of greater 8. The sun s 9 8. is produced when 10 nuclei fuse to make 11 nuclei. 9. Fusion releases even more energy than fission. 10. 11. Part B True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT. 12. Water is used as a moderator in nuclear reactors. 13. In nuclear fusion, the nuclei of two large atoms fuse together. Chapter 25 Nuclear Chemistry 665
14. Moderation of neutrons is used to slow nuclear fission. 15. Nuclear fusion can be easily produced under laboratory conditions. Part C Matching Match each description in Column B to the correct term in Column A. Column A Column B 16. fission 17. neutron moderation 18. neutron absorption a. the splitting of an atomic nucleus into smaller fragments b. combination of two nuclei to produce a nucleus of greater mass c. process used to reduce the speed of neutrons 19. fusion d. isotope capable of fission 20. uranium-235 e. process used to decrease the number of slow-moving neutrons Part D Questions and Problems Answer the following in the space provided. 21. How many neutrons are produced in each of the following fission reactions? 239 Pu 1 0 n 90 147 38Sr 56 Ba?1 0 n a. 94 b. 92 235 U 1 0 n 72 160 30Zn 62 Sm?1 0 n 22. What is the role in a nuclear reactor of a. neutron moderation? b. neutron absorption? 666 Core Teaching Resources
25.4 RADIATION IN YOUR LIFE Section Review Objectives Describe three devices that are used to detect radiation List examples of how radioisotopes are used in medicine Vocabulary ionizing radiation Geiger counter scintillation counter film badge neutron activation analysis Part A Completion Use this completion exercise to check your understanding of the concepts and terms that are introduced in this section. Each blank can be completed with a term, short phrase, or number. The radiation emitted by radioisotopes is known as 1 1. radiation because of its ability to strip 2 from atoms of a 2. bombarded substance. It is not possible to detect ionizing radiation 3. with your 3. 4. A 4 counter uses a 5 -filled tube to detect ionizing 5. radiation. A 6 counter uses a phosphor-coated surface to 6. detect 7 types of ionizing radiation. 7. Radioisotopes have many practical uses. For example, 8 8. is used to detect thyroid problems, while 9 is used to detect 9. skin cancers. 10 analysis is a procedure used to detect trace 10. amounts of elements in samples. Part B True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT. 11. The film badge is a personal radiation monitor. 12. A Geiger counter is the best alpha particle detector. Chapter 25 Nuclear Chemistry 667
13. A scintillation counter is used to detect gamma radiation. 14. Iodine-131 can detect thyroid problems. Part C Matching Match each description in Column B to the correct term in Column A. Column A 15. ionizing radiation 16. Geiger counter 17. scintillation counter 18. film badge 19. neutron activation analysis Column B a. radiation detector consisting of several layers of photographic film b. radiation with enough energy to knock electrons off some of the atoms it strikes c. device that uses a coated surface called a phosphor to detect ionizing radiation d. procedure used to detect trace amounts of elements in samples e. gas-filled tube used to detect radiation Part D Questions Answer the following in the space provided. 20. Which of the following is the best means of monitoring radiation for individuals who work with radioactive material? Circle the letter of the correct answer. a Geiger counter b. film badge c. scintillation counter 21. List applications of radioisotopes in research and medicine. 668 Core Teaching Resources