Nuclear ChemistryConstructive Response

Cyanide and Happiness

A paint sample of an “old painting” is found to

contain 0.010 g of 137Cs and 0.030 g of 137Ba.

1a) Write the nuclear equation for the decay of 137Cs

137 137 055 56 1Cs Ba + e

Question #1

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A paint sample of an “old painting” is found to

contain 0.010 g of 137Cs and 0.030 g of 137Ba.

1b) How old is the painting?

0.040 g Cs

0.020 g Cs

0.020 g Ba

0.010 g Cs

0.030 g Ba

Question #1

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A paint sample of an “old painting” is found to

contain 0.010 g of 137Cs and 0.030 g of 137Ba.

1c) What assumptions must be made when radio-dating?

Question #1

Question #2

Radioactivity and radioactive isotopes have the potential for both benefiting and harming living organisms. One use of radioactive isotopes is in radiation therapy as a treatment for cancer. Cesium-137 is sometimes used in radiation therapy.

A sample of cesium-137 was left in an abandoned clinic in Brazil in 1987. Cesium-137 gives off a blue glow because of its radioactivity. The people who discovered the sample were attracted by the blue glow and had no idea of any danger. Hundreds of people were treated for overexposure to radiation, and four people died.

2a) Using Reference Table N, complete the transmutation equation for Cs-137.

2a) Cs g e + Ba Click to reveal answer

12.5g25g50g100g

Question #2

Radioactivity and radioactive isotopes have the potential for both benefiting and harming living organisms. One use of radioactive isotopes is in radiation therapy as a treatment for cancer. Cesium-137 is sometimes used in radiation therapy.

A sample of cesium-137 was left in an abandoned clinic in Brazil in 1987. Cesium-137 gives off a blue glow because of its radioactivity. The people who discovered the sample were attracted by the blue glow and had no idea of any danger. Hundreds of people were treated for overexposure to radiation, and four people died.

2b) If 12.5 grams of the original sample of Cs-137 remained after 90.69 years, what was the mass of the original sample?

2b) First: = 3 half-lives Next: g g g

Answer: 100 g

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Question #2

Radioactivity and radioactive isotopes have the potential for both benefiting and harming living organisms. One use of radioactive isotopes is in radiation therapy as a treatment for cancer. Cesium-137 is sometimes used in radiation therapy.

A sample of cesium-137 was left in an abandoned clinic in Brazil in 1987. Cesium-137 gives off a blue glow because of its radioactivity. The people who discovered the sample were attracted by the blue glow and had no idea of any danger. Hundreds of people were treated for overexposure to radiation, and four people died.

2c) Suppose a 40 grams sample of Iodine-131 and a 40 gram sample of cesium-137 were both abandoned in the clinic in 1987. Explain why the sample of iodine-131 would not pose as great a radiation risk to people today as the cesium-137 would.

2c) I-131 has a half-life of 8.07 days, thus it will have almost completely decayed in the 20+ years that have gone by.

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Question #3

Some radioisotopes used as tracers make it possible for doctors to see images of internal body parts and observe their functions. The following table lists information about three radioisotopes and the body part each radioisotope is used to study.

3a) Complete 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.

3a) Fe g e + Co

Radioisotope

Half-life Decay Mode Body Part

24Na 15 hours Beta Circulatory system

59Fe 44.5 days Beta Red blood cells

131I 8.1 days Beta thyroid

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Question #3

Some radioisotopes used as tracers make it possible for doctors to see images of internal body parts and observe their functions. The following table lists information about three radioisotopes and the body part each radioisotope is used to study.

3b) 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 24Na remains unchanged after 60. hours?

3b) = four half lives, g g g g answer is:

Radioisotope

Half-life Decay Mode Body Part

24Na 15 hours Beta Circulatory system

59Fe 44.5 days Beta Red blood cells

131I 8.1 days Beta thyroid

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Question #4

A U-238 atom decays to a Pb-206 atom through a series of steps. Each point on the graph represents a nuclide and each arrow represents a nuclear decay mode.

4a) Based on this graph, what particle is emitted during the nuclear decay of a Po-218 atom?

4a) According to the graph, Po-218 experiences an alpha decay (note: the mass decreases by 4, and the proton amount decreases by 2).

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Question #4

A U-238 atom decays to a Pb-206 atom through a series of steps. Each point on the graph represents a nuclide and each arrow represents a nuclear decay mode.

4b) What are the two types of decay modes observed in the U-238 disintegration series, and indicate how many of each are observed.

4b) An atom of U-238 will experience 8 alpha decays (arrows down to left) and 6 beta decays (arrows to right) before it finally transmutates into

Pb-206.

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Question #4

A U-238 atom decays to a Pb-206 atom through a series of steps. Each point on the graph represents a nuclide and each arrow represents a nuclear decay mode.

4c) Explain why the U-238 disintegration series ends with

Pb-206.

4c) After the decays, the proton to neutron ratio in the Pb-206 are finally stable.

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Question #5

The radioisotopes carbon-14 and nitrogen-16 are present in a living organism.Carbon-14 is commonly used to date a once-living organism.

5a) Write an equation that represents the natural transmutation decay of C-14. Include both the atomic number and the mass number of all reactants and products.

5a) Click to reveal answer

Question #5

The radioisotopes carbon-14 and nitrogen-16 are present in a living organism.Carbon-14 is commonly used to date a once-living organism.

5b) Explain why N-16 is a poor choice for radioactive dating of a bone.

5b) The half-life for N-16 is too short (its decay rate is too quick)Click to reveal answer

Question #5

The radioisotopes carbon-14 and nitrogen-16 are present in a living organism.Carbon-14 is commonly used to date a once-living organism.

5c) A sample of wood is found to contain ⅛ as much C-14 as is present in the wood of a living tree. What is the approximate age, in years, of this sample of wood?

5c) 3(5715 y) or 17145 yearsClick to reveal answer

Question #6You may be surprised to learn that you do not need to visit a nuclear power plant or a

hospital X-ray laboratory to find sources of radioactivity. They are all around us. In fact, it is likely that you’ll find a few at home. Your front porch may incorporate cinder blocks or granite blocks. Both contain uranium. Walk through the front door, look up, and you’ll see a smoke detector that owes its effectiveness to the constant source of alpha particle emissions from Americium-241. As long as the gases remain ionized within the shielded container, electricity flows, and all is calm. When smoke enters the chamber, it neutralizes the charges on these ions. In the absence of these ions, the circuit breaks and the alarm goes off.

Indicator lights on your appliances may use Krypton-85; electric blankets, promethium-147; and fluorescent lights, thorium-229. Even the food we eat is radioactive. The more potassium-rich the food source, the more potassium-40—a radioactive isotope that makes up about 0.01% of the natural supply of this mineral—is present. Thus, brazil nuts, peanuts, bananas, potatoes, and flour, all rich in potassium, are radiation sources.

6a) Write the equation for the alpha decay that occurs in a smoke detector containing Americium-241 (Am-241).

6a) Click to reveal answer

Question #6You may be surprised to learn that you do not need to visit a nuclear power plant or a

hospital X-ray laboratory to find sources of radioactivity. They are all around us. In fact, it is likely that you’ll find a few at home. Your front porch may incorporate cinder blocks or granite blocks. Both contain uranium. Walk through the front door, look up, and you’ll see a smoke detector that owes its effectiveness to the constant source of alpha particle emissions from Americium-241. As long as the gases remain ionized within the shielded container, electricity flows, and all is calm. When smoke enters the chamber, it neutralizes the charges on these ions. In the absence of these ions, the circuit breaks and the alarm goes off.

Indicator lights on your appliances may use Krypton-85; electric blankets, promethium-147; and fluorescent lights, thorium-229. Even the food we eat is radioactive. The more potassium-rich the food source, the more potassium-40—a radioactive isotope that makes up about 0.01% of the natural supply of this mineral—is present. Thus, brazil nuts, peanuts, bananas, potatoes, and flour, all rich in potassium, are radiation sources.

6b) How is the radioactive decay of Krypton-85 different from the radioactive decay of Americium-241?

6b) Decay modes are different (beta decay vs alpha decay). Or half-life are different.Click to reveal answer

Question #6You may be surprised to learn that you do not need to visit a nuclear power plant or a

hospital X-ray laboratory to find sources of radioactivity. They are all around us. In fact, it is likely that you’ll find a few at home. Your front porch may incorporate cinder blocks or granite blocks. Both contain uranium. Walk through the front door, look up, and you’ll see a smoke detector that owes its effectiveness to the constant source of alpha particle emissions from Americium-241. As long as the gases remain ionized within the shielded container, electricity flows, and all is calm. When smoke enters the chamber, it neutralizes the charges on these ions. In the absence of these ions, the circuit breaks and the alarm goes off.

Indicator lights on your appliances may use Krypton-85; electric blankets, promethium-147; and fluorescent lights, thorium-229. Even the food we eat is radioactive. The more potassium-rich the food source, the more potassium-40—a radioactive isotope that makes up about 0.01% of the natural supply of this mineral—is present. Thus, brazil nuts, peanuts, bananas, potatoes, and flour, all rich in potassium, are radiation sources.

6c) State one benefit or useful application of radioactivity not mentioned in this article.

6c) Radioactivity can be used in medical diagnosis and/or treatment. Food irradiation Radioactive dating

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Question #6You may be surprised to learn that you do not need to visit a nuclear power plant or a

hospital X-ray laboratory to find sources of radioactivity. They are all around us. In fact, it is likely that you’ll find a few at home. Your front porch may incorporate cinder blocks or granite blocks. Both contain uranium. Walk through the front door, look up, and you’ll see a smoke detector that owes its effectiveness to the constant source of alpha particle emissions from Americium-241. As long as the gases remain ionized within the shielded container, electricity flows, and all is calm. When smoke enters the chamber, it neutralizes the charges on these ions. In the absence of these ions, the circuit breaks and the alarm goes off.

Indicator lights on your appliances may use Krypton-85; electric blankets, promethium-147; and fluorescent lights, thorium-229. Even the food we eat is radioactive. The more potassium-rich the food source, the more potassium-40—a radioactive isotope that makes up about 0.01% of the natural supply of this mineral—is present. Thus, brazil nuts, peanuts, bananas, potatoes, and flour, all rich in potassium, are radiation sources.

6d) State one risk or danger associated with radioactivity.

6d) Extensive exposure can make people sick. Contamination of environment Introduction of radioactive materials into the ecosystem

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Question #7In the 1920s, paint used to inscribe the numbers on watch dials was composed of a

luminescent (glow-in-the-dark) mixture. The powdered-paint base was a mixture of radium salts and zinc sulfide. As the paint was mixed, the powdered base became airborne and drifted throughout the workroom causing the contents of the workroom, including the painters’ clothes and bodies, to glow in the dark.

The paint is luminescent because radiation from the radium salts strikes a scintillator. Ascintillator is a material that emits visible light in response to ionizing radiation. In watch dial paint, zinc sulfide acts as the scintillator.

Radium present in the radium salts decomposes spontaneously, emitting alpha particles. These particles can cause damage to the body when they enter human tissue. Alpha particles are especially harmful to the blood, liver, lungs, and spleen because they can alter genetic information in the cells. Radium can be deposited in the bones because it substitutes for calcium.

7a) Write the notation for the alpha particles emitted by radium in the radium salts.

7a) Click to reveal answer

Question #7In the 1920s, paint used to inscribe the numbers on watch dials was composed of a

luminescent (glow-in-the-dark) mixture. The powdered-paint base was a mixture of radium salts and zinc sulfide. As the paint was mixed, the powdered base became airborne and drifted throughout the workroom causing the contents of the workroom, including the painters’ clothes and bodies, to glow in the dark.

The paint is luminescent because radiation from the radium salts strikes a scintillator. Ascintillator is a material that emits visible light in response to ionizing radiation. In watch dial paint, zinc sulfide acts as the scintillator.

Radium present in the radium salts decomposes spontaneously, emitting alpha particles. These particles can cause damage to the body when they enter human tissue. Alpha particles are especially harmful to the blood, liver, lungs, and spleen because they can alter genetic information in the cells. Radium can be deposited in the bones because it substitutes for calcium.

7b) How can particles emitted from radioactive nuclei damage human tissue?

7b) Emitted particles alter genetic information. Or Change DNAClick to reveal answer

Question #7In the 1920s, paint used to inscribe the numbers on watch dials was composed of a

luminescent (glow-in-the-dark) mixture. The powdered-paint base was a mixture of radium salts and zinc sulfide. As the paint was mixed, the powdered base became airborne and drifted throughout the workroom causing the contents of the workroom, including the painters’ clothes and bodies, to glow in the dark.

The paint is luminescent because radiation from the radium salts strikes a scintillator. Ascintillator is a material that emits visible light in response to ionizing radiation. In watch dial paint, zinc sulfide acts as the scintillator.

Radium present in the radium salts decomposes spontaneously, emitting alpha particles. These particles can cause damage to the body when they enter human tissue. Alpha particles are especially harmful to the blood, liver, lungs, and spleen because they can alter genetic information in the cells. Radium can be deposited in the bones because it substitutes for calcium.

7c) Why does radium substitute for calcium in bones?

7c) Both Group 2 metals OR Radium is a more active metal Similar chemical properties OR They are both alkaline earth metals It also has two valence electrons

Click to reveal answer

Question #7In the 1920s, paint used to inscribe the numbers on watch dials was composed of a

luminescent (glow-in-the-dark) mixture. The powdered-paint base was a mixture of radium salts and zinc sulfide. As the paint was mixed, the powdered base became airborne and drifted throughout the workroom causing the contents of the workroom, including the painters’ clothes and bodies, to glow in the dark.

The paint is luminescent because radiation from the radium salts strikes a scintillator. Ascintillator is a material that emits visible light in response to ionizing radiation. In watch dial paint, zinc sulfide acts as the scintillator.

Radium present in the radium salts decomposes spontaneously, emitting alpha particles. These particles can cause damage to the body when they enter human tissue. Alpha particles are especially harmful to the blood, liver, lungs, and spleen because they can alter genetic information in the cells. Radium can be deposited in the bones because it substitutes for calcium.

7d) Explain why zinc sulfide is used in luminescent paint.

7d) The paint acts as the scintillator OR The paint emits visible light in response to ionizing radiation. Click to reveal answer

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Question #8

The fossilized remains of a plant were found at a construction site. The fossilized remains contained the amount of carbon-14 that is present in a living plant.

8a) Determine the approximate age of these fossilized remains.

8a) Three half-lives have lapsed, notice the arrows: g g g Therefore, the plant fossils are 17145 years old (3 x 5715 years).

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Question #8

The fossilized remains of a plant were found at a construction site. The fossilized remains contained the amount of carbon-14 that is present in a living plant.

8b) Complete the nuclear equation for the decay of C-14. Your response must include the atomic number, the mass number, and the symbol of the missing particle.

8b) C g e + N Click to reveal answer