Chemistry Chapter 5 Nuclear Chemistry PDF

Karen Timberlake CHEMISTRY Thirteenth Edition, Global Edition Chapter 5 Nuclear Chemistry (Lecture PPTs) © 2019 Pearson E...

Karen Timberlake CHEMISTRY Thirteenth Edition, Global Edition Chapter 5 Nuclear Chemistry (Lecture PPTs) © 2019 Pearson Education Ltd.  5.1 Natural Radioactivity Unstable nuclei spontaneously emit small particles of energy called radiation to become more stable. Learning Goal Describe alpha, beta, positron, and gamma radiation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Natural Radioactivity Most naturally occurring isotopes of elements up to atomic number 19 have stable nuclei. Elements with atomic numbers 20 and higher usually have one or more isotopes that have unstable nuclei in which the nuclear forces cannot offset the repulsions between the protons. An unstable nucleus is radioactive, which means that it spontaneously emits small particles of energy called radiation to become more stable. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Radioisotopes A radioisotope has an unstable nucleus and emits radiation can be one or more isotopes of an element includes the mass number in its name Carbon-14, a radioactive isotope of carbon that is used for archeological dating, has a mass number of 14 and an atomic number of 6. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Stable and Radioactive Isotopes Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Types of Radiation Emitted Radioisotopes emit radiation such as alpha (a) particles, identical to a helium nucleus beta (β) particles, high-energy electrons positrons (β+) pure energy called gamma (γ) rays Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Alpha Particles An alpha (a) particle is identical to a helium nucleus has 2 protons and 2 neutrons has a mass number of 4 has a charge of 2+ has a low energy compared to other radiation particles Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Beta Particles A beta (β) particle is a high-energy electron has a mass number of 0 and a charge of 1− forms in an unstable nucleus when a neutron changes into a proton and an electron Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Positrons A positron (β+) has a mass number of 0 and a charge of 1+ forms in an unstable nucleus when a proton changes into a neutron and a positron Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Gamma Rays A gamma ray is high-energy radiation has a mass number of 0 and a charge of 0 is a form of energy emitted from an unstable nucleus to give a more stable, lower-energy nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Some Forms of Radiation Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Summary of Radiation Types When the nuclei of alpha, beta, positron, and gamma emitters emit radiation, new, more stable nuclei are produced. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Give the mass number and charge of each type of radiation. Mass Number Charge A. alpha particle 4 2+ B. positron 0 1+ C. beta particle 0 1− D. neutron 1 0 E. gamma ray 0 0 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Biological Effects of Radiation Ionizing radiation strikes molecules in its path. It damages the cells most sensitive to radiation: rapidly dividing cells in bone marrow, skin, and reproductive organs, and cancer cells. Cancer cells are highly sensitive to radiation; large doses of radiation are used to destroy them. The normal tissue around cancer cells divides at a slower rate and suffers less damage from radiation. Radiation may cause malignant tumors, leukemia, anemia, and genetic mutations. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Radiation Protection Radiation protection requires paper and clothing for alpha particles a lab coat or gloves for beta particles a lead shield or thick concrete wall for gamma rays limiting the amount of time spent near a radioactive source increasing the distance from the source Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Radiation Protection Different types of radiation In a nuclear pharmacy, a person working with penetrate the body to radioisotopes wears protective clothing and different depths. gloves and uses a lead glass shield on a syringe. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Radiation Protection Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Indicate the type of radiation (alpha, beta, and/or gamma) protection for each type of shielding. A. heavy clothing alpha, beta B. paper alpha C. lead alpha, beta, gamma D. lab coat alpha, beta E. thick concrete alpha, beta, gamma Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  5.2 Nuclear Reactions Nuclear equations use atomic symbols to show the changes in nuclear reactions. Learning Goal Write a balanced nuclear equation for radioactive decay, showing mass numbers and atomic numbers. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Radioactive Decay A process called radioactive decay an unstable nucleus spontaneously breaks down by emitting radiation is described by writing a nuclear equation Radioactive nucleus → new nucleus + radiation (α, β, β+, γ) Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Nuclear Equations In a balanced nuclear equation the sum of the mass numbers on each side of the equation must be the same the sum of the atomic numbers on each side of the equation must be the same Mass number sum: 251 = 251 251 Cf 98 96Cm + 2 He 247 4 Atomic number sum: 98 = 98 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Alpha Decay When a radioactive nucleus emits an alpha particle, a new nucleus forms with a mass number that is decreased by 4 and an atomic number that is decreased by 2. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Writing an Equation for Alpha Decay 23 Example: Write the balanced nuclear equation for the alpha decay of americium-241. STEP 1 Write the incomplete nuclear equation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Writing an Equation for Alpha Decay 24 Example: Write the balanced nuclear equation for the alpha decay of americium-241. STEP 2 Determine the missing mass number. STEP 3 Determine the missing atomic number. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Writing an Equation for Alpha Decay 25 Example: Write the balanced nuclear equation for the alpha decay of americium-241. STEP 4 Determine the symbol of the new nucleus. On the periodic table, the element that has atomic number 93 is neptunium, Np. The atomic symbol for this isotope of Np is written STEP 5 Complete the nuclear equation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Beta Decay A beta particle is an electron emitted from the nucleus when a neutron in the nucleus breaks down to form a proton and a beta particle, increasing the atomic number by 1. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Writing an Equation for Beta Decay Example: Write the balanced nuclear equation for the beta decay of yttrium-90, used in cancer treatment and as a colloidal injection into large joints to relieve the pain caused by arthritis. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Writing an Equation for Beta Decay Example: Write the balanced nuclear equation for the beta decay of yttrium-90. used in cancer treatment and as a colloidal injection into large joints to relieve the pain caused by arthritis. STEP 1 Write the incomplete nuclear equation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Writing an Equation for Beta Decay 29 Example: Write the balanced nuclear equation for the beta decay of yttrium-90. STEP 2 Determine the missing mass number. STEP 3 Determine the missing atomic number. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Writing an Equation for Beta Decay 30 Example: Write the balanced nuclear equation for the beta decay of yttrium-90. STEP 4 Determine the symbol of the new nucleus. On the periodic table, the element that has atomic number 40 is zirconium (Zr). The atomic symbol for this isotope of Zr is written. STEP 5 Complete the nuclear equation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Write the balanced nuclear equation for the beta decay of cobalt-60. ANALYZE THE Given Need Connect PROBLEM Co-60, balanced nuclear mass number, atomic beta decay equation number of new nucleus STEP 1 Write the incomplete nuclear equation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Write the balanced nuclear equation for the beta decay of cobalt-60. STEP 2 Determine the missing mass number. 60 =?+0 60 – 0 = ? 60 − 0 = 60 (mass number of new nucleus) STEP 3 Determine the missing atomic number. 27 =?−1 27 + 1 = ? 27 + 1 = 28 (atomic number of new nucleus) Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Write the balanced nuclear equation for the beta decay of cobalt-60. STEP 4 Determine the symbol of the new nucleus. On the periodic table, the element that has atomic number 28 is nickel (Ni). The atomic symbol for this isotope of Ni is written. STEP 5 Complete the nuclear equation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Positron Emission In positron emission, a proton is converted to a neutron and a positron the mass number of the new nucleus is the same, but the atomic number decreases by 1 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Gamma Emission In gamma emission, energy is emitted from an unstable nucleus, indicated by the symbol m following the mass number the mass number and the atomic number of the new nucleus are the same Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Producing Radioactive Isotopes Today, many radioisotopes are produced in small amounts by bombarding stable, nonradioactive isotopes with high-speed particles such as alpha particles, protons, neutrons, and small nuclei. When nonradioactive B-10 is bombarded by an alpha particle, the products are radioactive N-13 and a neutron. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Write the balanced nuclear equation for the bombardment of nickel-58 by a proton, which produces a radioactive isotope and an alpha particle. STEP 1 Write the incomplete nuclear equation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution 38 Write the balanced nuclear equation for the bombardment of nickel-58 by a proton, which produces a radioactive isotope and an alpha particle. STEP 2 Determine the missing mass number. STEP 3 Determine the missing atomic number. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution 39 Write the balanced nuclear equation for the bombardment of nickel-58 by a proton, which produces a radioactive isotope and an alpha particle. STEP 4 Determine the symbol of the new nucleus. On the periodic table, the element that has atomic number 27 is cobalt, Co. The atomic symbol for this isotope of Co is written STEP 5 Complete the nuclear equation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  5.3 Radiation Measurement A radiation counter is used to check radiation levels at the Fukushima Daiichi nuclear power plant. Learning Goal Describe the detection and measurement of radiation. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Geiger Counter A Geiger counter is a common instrument that detects beta and gamma radiation uses ions produced by radiation to create an electrical current Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Units for Measuring Radiation Units for measuring radiation activity include the following: curie (Ci)—the number of disintegrations that occurs in 1 s for 1 g of radium, equal to 3.7 × 1010 disintegrations/s becquerel (Bq)—the SI unit of radiation activity, which is 1 disintegration/s rad (radiation absorbed dose)—measures the amount of radiation absorbed by a gram of material such as body tissues rem (radiation equivalent in humans)—measures biological effects of different kinds of radiation Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Measuring Radiation Damage The rem (radiation equivalent in humans) measures alpha particles, which do not penetrate the skin; however, if they enter the body, extensive damage may occur in tissues high-energy radiation, which causes more damage than alpha particles and includes beta particles, high-energy protons, and neutrons that travel into tissue gamma rays, which are damaging because they travel a long way through body tissue Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Measuring Radiation Damage To determine the equivalent dose or rem dose, the absorbed dose (rad) is multiplied by a factor that adjusts for biological damage caused by a particular form of radiation. Biological damage (rem) = Absorbed dose (rad) × Factor For beta and gamma radiation, the factor is 1. For high-energy protons and neutrons, the factor is about 10. For alpha particles, the factor is 20. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Dosimeters Measure Radiation Exposure People who work in radiation laboratories wear dosimeters attached to their clothing. Dosimeters detect the amount of radiation exposure from the following: X-rays gamma rays beta particles Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Units of Radiation Measurement Often the measurement for an equivalent dose will be in millirems (mrem). 1 rem = 1000 mrem The SI unit is the sievert (Sv). 1 Sv = 100 rem he sievert (symbol: Sv) is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing radiation, which is defined as the probability of causing radiation-induced cancer and genetic damage. The Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Radiation Exposure The average person in the United States is exposed to 3.6 mSv of radiation annually. Exposure to radiation occurs every day from naturally occurring radioisotopes in buildings where we live and work food and water the air we breathe Sources of naturally occurring isotopes include the following: potassium-40 in potassium-containing foods cosmic radiation from the Sun Medical sources of radiation include X-rays and mammograms. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Average Annual Radiation Exposure in the United States Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Radiation Sickness Exposure to radiation of less than 0.25 Sv usually cannot be detected whole body exposure of 1 Sv produces a temporary decrease in the number of white cells of greater than 1 Sv may induce radiation sickness, causing nausea, vomiting, fatigue, and reduced white-cell counts Exposure to radiation of 5 SV is expected to cause death in 50% of the people receiving that dose. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Lethal Doses of Radiation The larger the dose of radiation received at one time, the greater the effect on the body. Exposure to radiation of 5 Sv is expected to cause death in 50% of the people receiving the dose. This amount of radiation to the whole body is called the lethal The LD50 for different life forms dose for one-half the population, or LD50. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Chemistry Link to Health Radiation and Food Foodborne illnesses caused by pathogenic bacteria such as Salmonella, Listeria, and Escherichia coli have become major health concerns in the United States. The U.S. Food and Drug Administration (FDA) has approved the use of 0.3 to 1 kGy of radiation produced by cobalt-60 or cesium- 137 for the treatment of foods. Cobalt pellets are placed in stainless steel tubes, arranged in racks. When food passes through a series of racks, gamma rays pass through the food and kill the bacteria. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Chemistry Link to Health Radiation and Food Currently, tomatoes, blueberries, strawberries, and mushrooms are being irradiated to allow them to be harvested when completely ripe and extend their shelf life. (a) The FDA requires this symbol to appear on irradiated retail foods. (b) After two weeks, the irradiated strawberries on the right show no spoilage. Mold is growing on the nonirradiated ones on the left. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Learning Check Match each property (1 to 3) with its unit of measurement (A to D). 1. activity A. mrad 2. absorbed dose B. mrem 3. biological damage C. becquerel D. Sv Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Match each property (1 to 3) with its unit of measurement (A to D). 1. activity C. becquerel 2. absorbed dose A. mrad 3. biological damage B. mrem, D. Sv Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  5.4 Half-Life of a Radioisotope The age of the Dead Sea Scrolls was determined using carbon-14. Learning Goal Given the half-life of a radioisotope, calculate the amount of radioisotope remaining after one or more half-lives. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Half-Life of a Radioisotope The half-life of a radioisotope is the time for the radiation level (activity) to decrease (decay) to one-half of its original value. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Decay Curve A decay curve is a diagram illustrating the decay of a radioactive isotope. The decay curve for iodine-131 shows that one-half of the radioactive sample decays and one-half remains radioactive after each half-life of 8 days. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Half-Lives of Radioisotopes Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Using Half-Lives of a Radioisotope Example: The radioisotope strontium-90 has a half-life of 38.1 yr. If a sample contains 36 mg of Sr-90, how many milligrams will remain after 114.3 yr? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Example: The radioisotope strontium-90 has a half-life of 38.1 yr. If a sample contains 36 mg of Sr-90, how many milligrams will remain after 114.3 yr? STEP 1 State the given and needed quantities. ANALYZE THE Given Need Connect PROBLEM 36 mg of Sr-90, milligrams of Sr-90 number of 114.3 yr elapsed, remaining half-lives half-life = 38.1 yr Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Example: The radioisotope strontium-90 has a half-life of 38.1 yr. If a sample contains 36 mg of Sr-90, how many milligrams will remain after 114.3 yr? STEP 2 Write a plan to calculate the unknown quantity. yearsHalf-life number of half-lives mg of Sr-90Number of mg of Sr-90 remaining half-lives Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Example: The radioisotope strontium-90 has a half-life of 38.1 yr. If a sample contains 36 mg of Sr-90, how many milligrams will remain after 114.3 yr? STEP 3 Write the half-life equality and conversion factors. 1 half-life 38.1 yr 38.1 yr 1 half-life and 1 half-life 38.1 yr Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Example: The radioisotope strontium-90 has a half-life of 38.1 yr. If a sample contains 36 mg of Sr-90, how many milligrams will remain after 114.3 yr? STEP 4 Set up the problem to calculate the needed quantity. 1 half-life 114.3 yr   3.00 half-lives 38.1 yr 1 half-life 2 half-lives 3 half-lives 36 mg     18 mg      9.0 mg      4.5 mg  4.5 mg of Sr-90 remain Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Learning Check Iodine-123, used in the treatment of thyroid, brain, and prostate cancer, has a half-life of 13.2 h. How much of a 64-mg sample of I-123 is left after 26.4 hours? A. 32 mg B. 16 mg C. 8.0 mg D. 4.0 mg Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Iodine-123, used in the treatment of thyroid, brain, and prostate cancer, has a half-life of 13.2 h. How much of a 64-mg sample of I-123 is left after 26.4 hours? STEP 1 State the given and needed quantities. ANALYZE THE Given Need Connect PROBLEM 64 mg of I-123, milligrams of I-123 number of 26.4 h elapsed, remaining half-lives half-life = 13.2 h Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Iodine-123, used in the treatment of thyroid, brain, and prostate cancer, has a half-life of 13.2 h. How much of a 64-mg sample of I-123 is left after 26.4 hours? STEP 2 Write a plan to calculate the unknown quantity. yearsHalf-life number of half-lives mg of I-123Number of mg of I-123 remaining half-lives Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Iodine-123, used in the treatment of thyroid, brain, and prostate cancer, has a half-life of 13.2 h. How much of a 64-mg sample of I-123 is left after 26.4 hours? STEP 3 Write the half-life equality and conversion factors. 1 half-life 13.2 h 13.2 h 1 half-life and 1 half-life 13.2 h Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Iodine-123, used in the treatment of thyroid, brain, and prostate cancer, has a half-life of 13.2 h. How much of a 64-mg sample of I-123 is left after 26.4 hours? STEP 4 Set up the problem to calculate the needed quantity. 1 half-life 26.4 h   2.00 half-lives 13.2 h 1 half-life 2 half-lives 64 mg     32 mg      16 mg 16 mg of I-123 remain The answer is B. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Chemistry Link to the Environment Dating Ancient Objects Radiological dating is a technique used by geologists, archaeologists, and historians to determine the age of ancient objects. The age of ancient objects is determined by measuring the amount of carbon-14 present. The age of a bone sample from a skeleton can be determined by carbon dating. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Chemistry Link to the Environment Dating Ancient Objects Carbon-14 is produced in the upper atmosphere by the bombardment of nitrogen-14 by high-energy neutrons from cosmic rays. Carbon-14 reacts with oxygen to form radioactive carbon dioxide which is absorbed by plants. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Chemistry Link to the Environment Dating Ancient Objects The uptake of carbon-14 in the CO2 stops when the plant dies. As the carbon-14 decays, the amount of radioactive carbon decreases. In a process called carbon dating, scientists use the half-life of carbon-14 (5730 yr) to calculate the length of time since the plant died. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  5.5 Medical Applications Using Radioactivity Chapter 16 Lecture Different radioisotopes are used to diagnose and treat a number of diseases. Learning Goal Describe the use of radioisotopes in medicine. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Medical Applications of Radioisotopes Radioisotopes with short half-lives are used in nuclear medicine because the cells in the body do not differentiate between nonradioactive atoms and radioactive atoms once incorporated into cells, the radioactive atoms are detected because they emit radiation, giving an image of an organ Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Radioisotopes in Medicine Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Learning Check Which of the following radioisotopes are most likely to be used in nuclear medicine? A. K-40 (half-life 1.3  109 yr) B. K-42 (half-life 12 h) C. I-131 (half-life 8 days) Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Which of the following radioisotopes are most likely to be used in nuclear medicine? Radioisotopes with short half-lives are used in nuclear medicine. A. K-40 (half-life 1.3  109 yr) Not likely: half-life is too long. B. K-42 (half-life 12 h) Short half-life, likely used. C. I-131 (half-life 8 days) Short half-life, likely used. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Scans with Radioisotopes After the patient receives a radioisotope, the scanner moves slowly across the body above the region where the organ containing the radioisotope is located the radiation technologist determines the level and location of radioactivity emitted by the radioisotope the gamma rays emitted from the radioisotope can be used to expose a photographic plate, producing a scan of the organ Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Scans with Radioisotopes A thyroid scan shows the accumulation of radioactive iodine-131 in the thyroid. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Positron Emission Tomography (PET) In positron emission tomography (PET), positron emitters with short half-lives are combined with body substances such as glucose positrons are used to study brain function, metabolism, and blood flow These PET scans show a normal brain on the left and a brain affected by Alzheimer’s disease on the right. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Positron Emission Tomography (PET) In positron emission tomography (PET), positrons are emitted from positron emitters such as carbon-11, oxygen-15, nitrogen-13, and fluorine-18 positrons combine with electrons to produce gamma rays are detected by computerized equipment to create a three- dimensional image of the organ Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Computed Tomography (CT) In computed tomography (CT), a computer monitors the absorption of 30 000 X-ray beams directed at successive layers of the target organ based on the densities of the tissues and fluids in the organ, the differences in absorption of the X- rays provide a series of images of the organ A CT scan shows a tumor (yellow) in the brain. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Magnetic Resonance Imaging (MRI) Magnetic resonance imaging (MRI) is an imaging technique that does not involve X-ray radiation is the least invasive imaging method available is based on the absorption of energy when protons in hydrogen atoms are excited by a strong magnetic field works because the energy absorbed An MRI scan provides images is converted to color images of the of the heart and lungs. body Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  5.6 Nuclear Fission and Fusion In the 1930s, scientists bombarding U-235 with neutrons discovered that the U-235 nucleus splits into two smaller nuclei and produces a large amount of energy. Learning Goal Describe the processes of nuclear fission and fusion. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Nuclear Fission In nuclear fission, a large nucleus is bombarded with a small particle the nucleus splits into smaller nuclei and several neutrons, releasing large amounts of energy, called atomic energy When a neutron bombards U-235, an unstable nucleus of U-236 undergoes fission (splits) smaller nuclei are produced such as Kr-91 and Ba-142 the neutrons emitted have high energy and bombard more U-235 nuclei Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Nuclear Fission A typical reaction for nuclear fission is: Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Missing Mass: E = mc2 If we could determine the mass of the products krypton, barium, and three neutrons, we would find that their total mass is slightly less than the mass of the starting materials the missing mass has been converted into an enormous amount of energy consistent with the famous equation derived by Albert Einstein: E = mc2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Chain Reaction In a nuclear chain reaction, the fission of each uranium-235 atom produces three neutrons that cause the nuclear fission of more and more uranium-235 atoms. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Chain Reaction A chain reaction occurs when a critical mass of uranium undergoes fission there is a rapid increase in the number of high-energy neutrons available to react with more uranium To sustain a nuclear chain reaction, sufficient quantities of U-235 must provide a critical mass in which almost all the neutrons immediately collide with more U-235 nuclei Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Nuclear Fusion Nuclear fusion occurs at extremely high temperatures (100 000 000 °C) combines small nuclei into larger nuclei releases large amounts of energy occurs continuously in the Sun and stars Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Nuclear Fusion In a fusion reaction, large amounts of energy are produced as hydrogen isotopes combine to form helium. Less waste is produced in a fusion reaction than in a fission reaction. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Chemistry Link to Environment Nuclear Power Plants In nuclear power plants, fission is used to produce energy the quantity of U-235 is held below its critical mass control rods in the reactor absorb neutrons to slow the fission process the heat produced in the fission process is used to make steam that drives a generator and Nuclear power plants supply about 20% of electricity in produces electricity the United States. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Chemistry Link to Environment Nuclear Power Plants Heat from nuclear fission is used to generate electricity. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Learning Check For each of the following, indicate whether it describes nuclear fission or nuclear fusion: A. A nucleus splits. B. Large amounts of energy are released. C. Small nuclei form larger nuclei. D. Hydrogen nuclei react. E. Several neutrons are released. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution For each of the following, indicate whether it describes nuclear fission or nuclear fusion: A. A nucleus splits. fission B. Large amounts of energy are released. fission and fusion C. Small nuclei form larger nuclei. fusion D. Hydrogen nuclei react. fusion E. Several neutrons are released. fission Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Learning Check Supply the missing atomic symbol to complete the equation for the following nuclear fission reaction: Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Solution Supply the missing atomic symbol to complete the equation for the following nuclear fission reaction: Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.  Concept Map Chemistry: An Introduction to General, Organic, and Biological Chemistry, Thirteenth Edition, Global Edition © 2019 Pearson Education Ltd.