Nuclear Chemistry Chapter 28 Assignment & Problem Set

Transcription

1 Nuclear Chemistry Name Warm-Ups (Show your work for credit) Date 1. Date 2. Date 3. Date 4. Date 5. Date 6. Date 7. Date 8.

2 Nuclear Chemistry 2 Study Guide: Things You Must Know Vocabulary (know the definition and what it means): nuclear chemistry isotope isotope notation mass number atomic number beta radiation alpha radiation gamma radiation elementary particle proton neutron electron positron alpha natural transmutation artificial transmutation radioisotope (nuclide) nuclear stability belt of stability beta emission positron emission Honors: electron capture alpha emission parent and daughter nucleus half-life half-life period radioactive dating radioactive tracer fission and fusion nuclear chain reaction Geiger counter scintillation counter Learning Objectives: what subatomic particles are in the nucleus how to write isotope notation showing the atomic number and mass number how to interpret the symbols and notations of particles using Table O how to determine the numbers of protons and neutrons in the nucleus given the notation of an isotope what types of radiation are emitted by a nucleus undergoing natural transmutation what types of nuclear radiation are most/least damaging to human tissue how to balance nuclear reactions and predict missing particles in nuclear reactions how to interpret the belt of stability how to predict the type of radiation emitted using belt of stability rules using atomic mass on the Periodic Table as a guide how to write balanced nuclear equations using Table N how to solve numerical problems involving half-life how artificial transmutation differs from natural transmutation uses of radioisotopes: carbon dating, medical applications, power generation, nuclear weapons the similarities and differences between nuclear fission and nuclear fusion how nuclear radiation is detected the essential differences between chemical reactions and nuclear reactions Reference Tables you should know how to interpret: Table N: Selected Radioisotopes Table O: Symbols Used in Nuclear Chemistry

3 Nuclear Chemistry 3 Read Chapter 28 Lab 28: Understanding Half-Life Regents Tables Table N: Selected Radioisotopes Table O: Symbols Used in Nuclear Chemistry Table T: Important Formulas and Equations Warm-ups and problems will be collected before you take the test. Answer all problems in the space provided. For problems involving an equation, carry out the following steps: 1. Write the equation. 2. Substitute numbers and units. 3. Show the final answer with units. There is no credit without showing work. Isotope Notation 1. How many protons, neutrons, and electrons are in atoms of each isotope. protons neutrons electrons iron-59 Fe-55 uranium-235 C-14 Th-234 Types of Radiation 2. Complete the table comparing alpha, beta, and gamma radiation. Symbol Mass Charge Damage to human tissue Alpha Beta Gamma Balancing Nuclear Reactions 3. Complete and balance the equations for the following nuclear reactions a. 13 Al + 2 He 14 Si +? c. 14 Si 0 1 +? b. 83 Bi 2 He +? d. 29 Cu 30 Zn +? Write an equation for the radioactive decay of fluorine-17 by positron emission.

4 Nuclear Chemistry 4 5. Write a nuclear equation for each word equation. a. Neon-19 undergoes positron decay. b. Kr-85 undergoes beta decay. c. Alpha radiation is emitted during the disintegration of uranium Write a nuclear equation for the decay of each of the following radioisotopes. a. Carbon-14. b. Radon-222 c. I What isotope remains after three beta particles and five alpha particles are lost from a thorium-234 isotope? Belt of Stability and Predicting Nuclear Reactions 8. What is meant by the belt of stability? 9. What happens to an isotope that falls outside the band of stability? 10. Explain the difference between an isotope and radioisotope. 11. Identify the more stable isotope in each pair. a. C-14, C-13 b. H-1, H-3 c. O-16, O-18 d. N-15, N-14 e. K-40, K-39

5 Nuclear Chemistry How are mass number and atomic number of a nucleus affected by the loss of the following? a. beta particle b. alpha particle c. gamma rays 13. Using the belt of stability, predict the mode of decay and write balanced nuclear equations for the decay of: a. Zr-97 b. Th-230 Half-Life 14. Explain half-life. 15. Manganese-56 is a beta emitter with a half-life of 2.6 h. What is the mass of manganese-56 in a 1.0 mg sample of the isotope at the end of 10.4h? 16. The mass of thorium 234 in a sample is found to have decreased from 0.800g to 0.100g in a period of 72.3 days. From this information, calculate the half-life of thorium A patient is administered 20 mg of iodine-131. How much of this isotope will remain in the body after 40 days? 18. For the decay of Fr-220: a. Write a balanced nuclear equation. b. What is the half-life?

6 Nuclear Chemistry 6 c. If you start with 72 g of Fr-220, how much is left after 1.83 minutes? 19. For the decay of Co-60, used for treating cancer, what percent of Co-60 remains after 7 half-lives? Transmutation 20. What is the difference between natural and artificial decay? 21. Give an example nuclear equation for the synthesis of a transuranium element by artificial transmutation. Uses of Radioactive Isotopes 22. What is a radioactive tracer? 23. What types of radiation can be detected using a Geiger counter? A scintillation counter? 24. Why is it important that radioactive isotopes used internally for medical diagnosis or treatment have relatively short half-lives? 25. Explain how iodine-131 is used to treat thyroid disease. Fission and Fusion 26. Define fission and define fusion. Which is currently used as a reliable source of energy? 27. Where does fusion occur naturally? 28. What equation is used to calculate the energy that comes from both fission and fusion? Define all terms in the equation.

7 Nuclear Chemistry Assuming technical problems could be overcome, what are some advantages to producing electricity in a fusion reactor? Review 30. Balance the following equations. a. Ca(OH) 2 + HCl CaCl 2 + H 2O b. Fe 2O 3 + H 2 Fe + H 2O c. NaHCO 3 + H 2SO 4 Na 2SO 4 + CO 2 + H 2O d. C 2H 6 + O 2 CO 2 + H 2O 31. You have a 0.30M solution of sodium sulfate. What volume in ml must be measured to give mol of sodium sulfate? 32. Identify the bonds between each pair of atoms as ionic (I) or covalent (C). a. carbon and silicon b. calcium and fluorine c. sulfur and nitrogen d. bromine and cesium 33. How many liters of hydrogen gas (at STP) will be produced when g of magnesium metal reacts with an excess of sulfuric acid? First write a balanced chemical equation.

8 Nuclear Chemistry 8 Using the Belt of Stability to Predict Nuclear Reactions The best way to understand nuclear decay is determine which combinations of protons and neutrons in a nucleus are stable. This relationship can be viewed by plotting the number of neutrons (y-axis) vs. number of protons (xaxis) as shown in the figure below. The dark-shaded area in the figure is called the belt of stability, which represents all combinations of protons and neutrons that lead to a stable nucleus. All other combinations of protons and neutrons give nuclei that are not stable, called radioisotopes, that will turn into a different element accompanied by emission of radiation. Belt of Stability Several generalizations can be made by looking at the plot. 1. For low atomic numbers, up to about the element calcium, stable nuclei have equal numbers of protons and neutrons. 2. For higher atomic numbers, stable nuclei have greater numbers of neutrons than protons. 3. All elements with atomic number greater that 82 (Pb) are unstable. Modes of Nuclear Decay The unstable regions on the plot can be broken into three areas, A, B, and C, each with its own modes of decay. Region A (too many neutrons leads to beta emission): This region decays by turning a neutron in the nucleus into a proton, accompanied by the emission of a beta particle (electron). 1 0 n p + e - 1 example of beta emission: 40 K Ca + e

9 Nuclear Chemistry 9 Region B (too few neutrons leads to either positron emission or electron capture): This region can decay by two different modes, positron emission or electron capture. For positron emission, a proton in the nucleus turns into a neutron accompanied by the emission of a positron. 1 1 p n + 1 e example of positron emission: 38 K Ar + e The other possible decay in region B is electron capture, where an electron orbiting the nucleus is captured by the nucleus. example of electron capture: 37 Ar e 17 Cl Region C (too many protons and neutrons leads to alpha emission): Very large nuclei give off an alpha particle in order to reduce their mass. example of alpha emission: 238 U Th A last tip: Often you can predict the mode of decay by comparing the mass number of the nucleus to the average atomic mass of that element found on the periodic table. For example, the isotope K-40 is more massive than the average mass for K found on the period table (39.1 amu). Thus one could rightly guess that K-40 would decay by beta emission (region A). Summary: Modes of Decay Region Isotope Compared to Periodic Table Modes of Decay A: too many n Mass number of isotope is greater (above belt of stability, and beta emission than mass on Periodic Table atomic numbers 1-82) B: too few n (below belt of stability, and atomic numbers 1-82) C: too many n & p + (past belt of stability) Mass number of isotope is less than mass on Periodic Table Atomic number greater than 82 (Pb) positron emission alpha emission