Presentation on theme: "Chemistry 142 Chapter 19: Radioactivity and Nuclear Chemistry Outline I.Types of Radiation II.Nuclear Equations III.Radioactive Decay IV.Applications."— Presentation transcript:
Chemistry 142 Chapter 19: Radioactivity and Nuclear Chemistry Outline I.Types of Radiation II.Nuclear Equations III.Radioactive Decay IV.Applications of Radioactivity
Tro, Chemistry: A Molecular Approach 2 Image left by uranic rays
Types of Radiation and Their Penetrating Abilities 0.01 mm 1 mm 100 mm Pieces of Lead
Types of radioactive decay alpha particle emission
Types of radioactive decay beta emission
Types of radioactive decay positron emission
Biological Effect of Radiation
Tro, Chemistry: A Molecular Approach 12 Valley of Stability for Z = 1 20, stable N/Z 1 for Z = 20 40, stable N/Z approaches 1.25 for Z = 40 80, stable N/Z approaches 1.5 for Z > 83, there are no stable nuclei
Tro, Chemistry: A Molecular Approach 15 U-238 Decay Series or or other combinations
Detecting Radioactivity Film Badge Electroscope Tro, Chemistry: A Molecular Approach16 +++
Tro, Chemistry: A Molecular Approach 18 Half-Life of a First-Order Reaction Is Constant
Chapter 19 – Nuclear Chemistry Example – Half-Life 19.1Technetium-99m is used to form pictures of internal organs in the body; Particularly to assess heart damage. The rate constant, k, for Tc-99m is 1.16 x hr -1, what is the half-life?
Chapter 19 – Nuclear Chemistry Example – Half-Life 19.2The half-life of molybdenum-99 is 67.0 hours. How much of a mg sample of Mo-99 is left after 335 hours?
Chapter 19 – Nuclear Chemistry Example – Half-Life 19.3Sodium-24 decays by positron emission, has a half-life of 60 hours, and an atomic mass of amu. Suppose that a patient is injected with 80. mg of sodium-24 to measure their sodium electrolyte balance. a.How much remains after 75 hours? b.How many positron emissions occur in 75 hours? c.What dose of radiation (in Ci) is the person exposed to?
Radiocarbon Dating of Artifacts
Calibration Curves for Radiocarbon Dating
Chapter 19 – Nuclear Chemistry Example – Radioactive Dating 19.4The remnants of an ancient fire in a cave in Africa showed a carbon-14 decay rate of 3.1 counts per minutes per gram of carbon. Assuming that the decay rate of carbon-14 in freshly cut wood is 13.6 counts per minutes per gram of carbon, calculate the age of the remnants (t 1/2 C-14 is 5730 years).
Chapter 19 – Nuclear Chemistry Example – Radioactive Dating 19.5A rock containing uranium-238 and lead-206 was examined to determine its approximate age. Analysis showed the ratio of lead-206 atoms to uranium-238 atoms to be Assuming no lead was originally present, that all the lead-206 formed over the years has remained in the rock and that the number of nuclides in intermediate stages of decay between uranium-238 and lead-206 is negligible, calculate the age of the rock (t 1/2 U-238 is 4.5 x 10 9 years).
Fission Tro, Chemistry: A Molecular Approach26
Nuclear Fission U + 1 n 90 Sr Xe n + Energy Representative fission reaction
Tro, Chemistry: A Molecular Approach 28 Tokamak Fusion Reactor
Tro, Chemistry: A Molecular Approach 29 Cyclotron
Tro, Chemistry: A Molecular Approach 30 Linear Accelerator
Chapter 19 – Nuclear Chemistry Example – Binding Energy 19.6Calculate the binding energy per nucleon for the helium-4 nucleus. Given the atomic mass of helium-4 is amu, a proton is x g and a neutron is x g. (1 amu = x g)
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Fat Man and Little Boy
Nuclear Power Use
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39 PLWR Core Containment Building Turbine Condenser Cold Water Boiler
40 PLWR - Core Cold Water Fuel Rods Hot Wate r Control Rods
Sources of Radiation
Quantities of Radiation UnitParameterDescription Curie (Ci) Level of Radioactivity 3.7x10 10 nuclear disintegrations/s Becquerel (B)* Level of Radioactivity 1 disintegration/s Gray (Gy) Ionizing Energy Absorbed 1 Gy = 1 J/kg of tissue mass Sievert (Sv) Amount of Tissue Damage 1Sv = 1Gy x RBE** *SI unit of radioactivity **Relative Biological Effectiveness
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Physiological Effect of a Single Dose of Radiation Dose (rem)Dose (Sv)Likely Effect No observable effect White blood cell count decreases slightly Significant drop in white blood cell count, lesions Nausea, vomiting, loss of hair Hemorrhaging, ulcers, possible death >500>5Death
IsotopeSymbolDecayHalf-LifeUse tritium 3H3H y Biochemical tracer carbon C 5715 y Archaeological Dating phosphorus P d Leukemia Therapy potassium K 1.26×10 9 y Geologic Dating cobalt Co 5.27 y Cancer Therapy iodine I 13.1 h Thyroid Therapy uranium U, 7.04×10 8 yNuclear Reactors
Tro, Chemistry: A Molecular Approach 50 Medical Applications of Radioisotopes Bone Scan with 99m Tc Brain images with 123 I- labeled compound
Chemistry In Action: Food Irradiation DosageEffect Up to 100 kilorad Inhibits sprouting of potatoes, onions, garlics. Inactivates trichinae in pork. Kills or prevents insects from reproducing in grains, fruits, and vegetables. 100 – 1000 kilorads Delays spoilage of meat poultry and fish. Reduces salmonella. Extends shelf life of some fruit to 10,000 kilorads Sterilizes meat, poultry and fish. Kills insects and microorganisms in spices and seasoning.
Applications – Chemical Analysis Radioactive tracer – used to follow fate of a chemical using radio labeling Isotopic dilution – used to determine quantity of a substance when you cant measure it conveniently Neutron Activation Analysis – used to determine concentration of trace elements
Applications Medicine – Diagnostic tracers PET – Positron Emission Tomography Patient fed radio-labeled glucose and it goes to where there is lots of metabolic activity. This often indicates a region of tumor activity. – Chemotherapy – Power pacemakers