2) Explain why the U-238 disintegration series shown in the graph ends with the nuclide Pb-206.

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Hector Watts
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1 Name: Page 1 Questions 1 and 2 refer to the following: A U-238 atom decays to a Pb-206 atom through a series of steps. Each point on the graph below represents a nuclide and each arrow represents a nuclear decay mode. 1) Based on the graph shown, what particle is emitted during the nuclear decay of a Po-218 atom? 2) Explain why the U-238 disintegration series shown in the graph ends with the nuclide Pb-206. Questions 3 and 4 refer to the following: The radioisotope uranium-238 occurs naturally in Earth's crust. The disintegration of this radioisotope is the first in a series of spontaneous decays. The sixth decay in this series produces the radioisotope radon-222. The decay of radon-222 produces the radioisotope polonium-218 that has a half life of 3.04 minutes. Eventually, the stable isotope lead-206 is produced by the alpha decay of an unstable nuclide.

2 Page 2 3) Using the given information, complete the nuclear equation below for the decay of the unstable nuclide that produces Pb-206, by writing a notation for the missing nuclide. 4) Using the given information, determine the original mass of a sample of Po-218, if 0.50 milligram of the sample remains unchanged after minutes. 5) Complete the nuclear equation below. Include the symbol, atomic number, and mass number for the missing particle. Questions 6 through 8 refer to the following: When a uranium-235 nucleus absorbs a slow-moving neutron, different nuclear reactions may occur. One of these possible reactions is represented by the complete, balanced equation below. For this reaction, the sum of the masses of the products is slightly less than the sum of the masses of the reactants. Another possible reaction of U-235 is represented by the incomplete, balanced equation below. 6) Write a notation for the missing product in equation 2 in the given reading passage. 7) Identify the type of nuclear reaction represented by equation 1 in the given reading passage.

3 8) Based on the reading passage, determine the half-life of the krypton-92 if only 6.0 milligrams of an original 96.0-milligram sample remains unchanged after 7.36 seconds Page 3 Questions 9 and 10 refer to the following: Scientists are investigating the production of energy using hydrogen-2 nuclei (deuterons) and hydrogen-3 nuclei (tritons). The balanced equation below represents one nuclear reaction between two deuterons. 9) State, in terms of subatomic particles, how the deuteron used in the given investigation differs from the triton. 10) Identify the type of nuclear reaction represented by the equation in the given investigation. 11) Determine the total time that must elapse until only of an original sample of the radioisotope Rn-222 remains unchanged. Questions 12 and 13 refer to the following: In living organisms, the ratio of the naturally occurring isotopes of carbon, C-12 to C-13 to C-14, is fairly consistent. When an organism such as a woolly mammoth died, it stopped taking in carbon, and the amount of C-14 present in the mammoth began to decrease. For example, one fossil of a woolly mammoth is found to have living organism. of the amount of C-14 found in a

4 Page 4 12) Identify the type of nuclear reaction that caused the amount of C-14 in the woolly mammoth mentioned in the reading passage to decrease after the organism died. 13) Determine the total time that has elapsed since the woolly mammoth mentioned in the reading passage died. 14) Some radioisotopes used as tracers make it possible for doctors to see the images of internal body parts and observe their functions. The table below lists information about three radioisotopes and the body part each radioisotope is used to study. Based on the given data, write the equation for the nuclear decay of the radioisotope used to study red blood cells. [Include both the atomic number and the mass number for each missing particle.] 15) Cobalt-60 is commonly used as a source of radiation for the prevention of food spoilage. Bombarding cobalt-59 nuclei with neutrons produces the nuclide cobalt-60. A food irradiation facility replaces the cobalt-60, a source of gamma rays, when the radioactivity level falls to of its initial level. The nuclide cesium-137 is also a source of radiation for the prevention of food spoilage. Identify one emission spontaneously released by the cobalt-60 nucleus described.

5 Page 5 16) 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 halflife 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. Based on the given information, state one scientific reason why Am-241 is a more appropriate radioactive source than Fr-220 in an ionizing smoke detector. 17) The fossilized remains of a plant were found at a construction site. The fossilized remains contain the amount of carbon-14 that is present in a living plant. Complete the nuclear equation provided below for the decay of C-14. Your response must include the atomic number, the mass number, and the symbol of the missing particle.

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

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