A. Identify the highly penetrating radioactive emission that exposed the photographic plates.

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1 Name Unit 3: Nuclear Chemistry Date Part 2 Questions 1. In 1896, Antoine H. Becquerel discovered that a uranium compound could expose a photographic plate wrapped in heavy paper in the absence of light. It was shown that the uranium compound was spontaneously releasing particles and high-energy radiation. Further tests showed the emissions from uranium that exposed the photographic plate were not deflected by charged plates. A. Identify the highly penetrating radioactive emission that exposed the photographic plates. B. Write the nuclear equation for the alpha decay of U-238. C. Determine the number of neutrons in an atom of U-233. D. Identify the type of nuclear reaction that occurs when an alpha or a beta particle is spontaneously emitted by a radioactive isotope. 2. Nuclear radiation is harmful to living cells, particularly fast growing cells, such as cancer cells and blood cells. An external beam of the radiation emitted from a radioisotope can be directed on a small area of a person to destroy cancer cells within the body. Cobalt-60 is an artificially produced radioisotope that emits gamma rays and beta particles. One hospital keeps a 100 gram sample of Co-60 in a secure storage container for future cancer treatment. A. Compare the penetrating power of the two emissions from Co-60. B. Write the equation for the beta decay of Co-60. C. Determine the total time that will have elapsed when 12.5 grams of the original Co-60 sample at the hospital remains unchanged.

2 3. Polonium-210 can be created in the laboratory by bombarding bismuth-209 with neutrons to create bismuth-210. The Bi-210 undergoes beta decay to produce Po-210. Po-210 has a half-life of 138 days and undergoes alpha decay. A. Write the nuclear equation for the decay of Po-210. B. Determine the total mass of an original 28 mg sample of Po-210 that remains unchanged after 414 days. 4. An original sample of fluorine-21 had a mass of 80 mg. Only 20 mg of this original sample remain unchanged after 8.32 seconds. What is the half-life of fluorine-21? 5. What was the original mass of a radioactive sample that decayed to 25 grams in four halflife periods? 6. A battery-operated smoke detector produces an alarming sound when its electrical sensor detects smoke particles. Some ionizing smoke detectors contain the radioisotope americium-241, which undergoes alpha decay and has a half-life of 433 years. The emitted alpha particles ionize gas molecules in the air. As a result, an electric current flows through the detector. When smoke particles enter the detector, the flow of ions is interrupted, causing the alarm to sound. A. State one scientific reason why Am-241 is a more appropriate radioactive source than Fr-220 in an ionizing smoke detector.

3 B. Write the nuclear equation for the decay of Am-241. C. What fraction of Am-241 would remain in a smoke detector after 1,299 years? 7. Scientists are investigating the production of energy using hydrogen-2 nuclei and hydrogen-3 nuclei. The balanced equation below represents one nuclear reaction between two hydrogen-2 nuclei. A. Identify the type of reaction represented by the equation. B. Explain, in terms of both reactants and products, your answer to Part A. C. List two requirements that must be met for the above reaction to occur. Explain. 8. Nuclear weapons were tested in the atmosphere until a treaty banning this procedure was signed in The explosion of these fission reaction devices produced radioactive wastes which still contaminate our environment today. One of the radioactive isotopes produced by these explosions was strontium-90, a group 2 element. Strontium-90 can be ingested by humans and absorbed into their skeletal system. Absorbed inside, it can undergo beta decay and produce harmful effects. A. Write the nuclear equation for the decay of Sr-90.

4 B. How is the radioactive decay of Sr-90 different from the radioactive decay of U-235, also used in nuclear weapons? 9. One possible reaction of plutonium-239 is shown below. A. Identify the decay mode of the plutonium-239 radioisotope. B. Identify the type of reaction shown above. C. Write the notation for the missing product represented by X. D. Compare the amount of energy released in the reaction above to the amount of energy released by the complete combustion of methane. 10. Some radioisotopes used as tracers make it possible for doctors to see images of internal body parts and observe their function. The table below lists information about three radioisotopes and the body part each radioisotope is used to study. A. It could take up to 60 hours for a radioisotope to be delivered to the hospital from the laboratory where it is produced. What fraction of an original sample of 24 Na remains unchanged after 60 hours?

5 B. Write the equation for the nuclear decay of the radioisotope used to study red blood cells. C. Complete the table by identifying the body part that 131 I is used to study. 11. A. State one possible advantage of using nuclear power instead of burning fossil fuels. B. State one possible risk of using nuclear power. C. If animals feed on plants that have that have taken up Sr-90, the Sr-90 can find its way into their bone structure. Explain one possible danger to the animals.