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Ch. 26 Nuclear Chemistry

Ch. 26 Nuclear Chemistry. vs. Nuclear Rxns. No new _______ can be produced Only the e - participate Relatively small amounts of energy are _______ or _______ Rate of rxn depends on _______ such as concentration, temperature, catalysts, and pressure.

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Ch. 26 Nuclear Chemistry

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  1. Ch. 26 Nuclear Chemistry

  2. vs. Nuclear Rxns • No new _______can be produced • Only the e- participate • Relatively small amounts of energy are _______ or _______ • Rate of rxn depends on _______ such as concentration, temperature, catalysts, and pressure. • Elements may be converted from one _______ to _______ . • Particles _______ the nucleus are involved. • Tremendous amounts of energy are _______ or _______ • Rate of rxn is not influenced by _______ factors Ordinary Chemical Rxns

  3. Nuclide too large – ____or Too many neutrons _______(electron) or Too many protons, _______(also called a positron or electron capture) or Several types of radioactive decay Nuclear particles

  4. Neutron • Proton or • Gamma (high energy including x-rays) • heavy proton Other types of particles used during radioactive decay

  5. For the general reaction The two conservation principles demand A1 = A2 + A3 and Z1 = Z2 + Z3 • A's are atomic mass numbers • Z's are atomic numbers Balancing Nuclear Rxns

  6. A beta particle is an electron _______ from the nucleus when a neutron is converted to a proton. β emission = electron 1n = 1p + -1β 228Ra -1β + 228Ac 14C 14N + -1β Beta Emission

  7. +1β = positron 1p 1n + +1β 38K 38Ar + +1β 15O 15N + +1β K capture 106Ag + -1e 106Pd 37Ar + -1e 37Cl Positron emission or electron capture (___________)

  8. Alpha emission 4α or 4He 204Pb 200 Hg + 4α All nuclides with atomic # greater than ___are radioactive. Most decay by _______ emission *only stable nuclide with atomic # 83 is 209Bi Alpha emission

  9. 83+ protons  alpha decay • neutron rich  β emission • neutron poor  K capture or positron emission Types of Nuclear Rxns

  10. Radiation Interaction with Matter

  11. 1896 - ______________–discovers radioactivity in U salts • 1898 - _______ and _______Curie–discover two new radioactive elements, Po and Ra • 1898 - ________________ –discovers that radioactivity has two forms: α and β radiation History

  12. ~ _______ have a stabilizing effect on proton – proton _______ • ~ neutrons and protons swap particles called _______ which keeps the atom together • ~ as # of protons increases, atoms need even _______ neutrons. Belt of stability

  13. – Δm – for a nucleus is the difference between the sum of the _______ of e-, p+ and no in the atom and the _______ measured _______ of the atom. Table 26-1 • Δm = (sum of all e-, p+ and no) – (actual mass of the atom) • 1 amu = 1.661 x 10-24 grams Mass deficiencyΔm

  14. Ex. 1) Calculate the mass deficiency for 39K in amu/atom and in g/mol. The actual mass of 39K is 39.32197 amu per atom Example Problem

  15. (BE) provides the powerful short-range force that holds the nuclear particles together in a small volume. • _______EinsteinsE = mc2 Nuclear binding energy

  16. Ex. 2) Use the value for Δm39 K to calculate the nuclear binding energy in J/mol of K atoms. 1J = 1kg m2/s2.

  17. Both processes generate large amounts of energy Nuclear fission • splitting of a heavy nucleus into two lighter nuclei Nuclear fusion • combining two light nuclei into one heavier nucleus Fission and Fusion

  18. (fuse – put together) _______ nuclei into _______ ones. • Extremely high energies or temperatures are necessary to initiate fusion reactions. Ex. Stellar energy source is fusion (stars) • ~ still a mass loss E = mc2 • ~ fusion typically uses H as a fuel 1H ~ Hydrogen (protium) 2H~ Heavy H (deuterium) 3H~ tritium • 2H+ 2H 3H + 1H Fusion

  19. Fusion _______ – Why? ~ no chance of ______________ ; no radioactive products; Hydrogen is easy to get (75% of universe is Hydrogen); _______ ; and fusion produces _______ energy per amu. • Bad – Why? ~ _______extreme heat and harder to do.

  20. occurs when _______ nuclei break down into _______ ones. Ex. U, Th, Pa, Pu, • Some fission rxns are spontaneous while others require activation by neutron bombardment • Very _______ – chain reaction - mass goes down and energy is produced. • Controlled at Nuclear Power Plants pg 1027. ~ know the different parts • Reactors, Fuel, Moderator, Control Rods, Cooling Systems, and Shielding Fission

  21. Pressurizes water reactor Boling water reactorPWR ~ 2000 psi BWR ~ 1000 psi

  22. –Three Mile Island, PA(_______ ) Nuclear reactor malfunctioned – no meltdown, but some radioactive contamination. Affected a 25 mile radius • –Chernobyl , Russia(_______ ) Nuclear reactor’s cooling system failed – meltdown. Released thirty times the radioactivity of the atomic bombs dropped on Hiroshima and Nagasaki. 31 lives were lost immediately. Radiation in soil & atmosphere still presents significant health risks. • One of the main concerns: Acute radiation to cells causes them to divide and grow without control – this creates a tumor (cancer) *More harmful to children than adults Nuclear Power Plant accidents

  23. Japan (_______ ) After the earthquake and tsunami that hit Japan in 2011. The cooling system of the nuclear power plant in Fukushima failed causing the reaction to spiral out of control. The heat produced by the reaction caused the Uranium to decay to Cesium 137, a very unstable atom that caused most of the environment to become radioactive. This has caused the area to become a dead zone.

  24. Fission Fusion Merge (makes heavier products) Release tremendous amounts of energy Produces no radioactive waste Hydrogen + Hydrogen  Helium Involves changes in the atom at the subatomic level Currently not feasible Split up (makes lighter products) Release tremendous amounts of energy Produces radioactive waste Uranium  lots of smaller radioactive elements Involves changes in the atom at the subatomic level Used at nuclear reactors

  25. Radiation & radioactive materials can be used in a number of ways. The following merely touches on the subject: • Agriculture - The increase in the volume and quality of grains & cereals has been vastly improved by growing superior strains labeled with radioactive isotopes.  These improvements are helping to alleviate famine in third world countries. Benefits of Nuclear Radiation

  26. Cancer Treatments - Cancerous cells can be selectively killed by the use of radioactivity, either in the form of directed beams, as for breast cancer, or as radioactive bullets that are designed to migrate directly to the cancerous cells that need killing.  • Chemotherapy, one of the only current alternatives, which involves the use of invasive drugs, but it is very difficult for the patient.

  27. Environmental Measurements - The movement of pollutants through the environment (ex. ground water and rivers)- can be accurately measured by the use of radioactive tracers. • Food - Food, such as beef and chicken, that has been sterilized by irradiation(the process of being exposed to radiation) has a longer shelf life and is free of E. coli ~ a bacterium that can kill as a result of eating poorly cooked food. (children are more susceptible to E. coli than adults) • An extension of food irradiation could save the lives of many children and would be particularly useful in developing countries where refrigeration is not available.

  28. Generation of Electricity - Over 440 nuclear plants around the world contribute some 16% of the world's electrical energy needs.  109 plants in the U.S. contributed 22% of the US's consumption of electricity in 2000. • Medical Diagnostics - The use of radiation in the medical world extends from X-rays, through magnetic resonance imaging (MRI), to the use of radioactive tracers to diagnose such varied conditions as faulty thyroid glands or bone problems.  The use of radioactive tracers often replaces the use of invasive surgical diagnosis.

  29. Polymerization of Plastics - Plastics can be polymerized by radiation instead of damaging heat treatments.  The polymerized plastics are used in such applications as car dashboards, which would, otherwise, crack badly under heat in the summer. • Quality Control of Metal Parts - The integrity of metal parts such as aircraft engine blades can be verified by radiophotography on a conveyor belt instead of having to destroy a sampling of blades to ensure they are intact.

  30. Research in Biology - The use of radioactive tracers allows the non-invasive tracking of elements and drugs through the body for both metabolic studies and medicine. • Space Power - When small amounts of power are needed in space in regions where solar power is inefficient (on the dark side of the moon or when large solar panels are impossible), plutonium batteries are ideal producers of compact energy.

  31. ____________ turn into other elements • the closer they are to the Belt of stability, the _______ it takes • every single nuclide has a different rate of decay, we measure the different rates of decay with half-life. • Half-life: the time it takes for _______of the nuclei to _______ into something else. Radioactive Half-lives and Decay

  32. ______________can be used to estimate the ages of items of organic origin. 14C is produced continuously in the upper atmosphere by the bombardment of 14N by cosmic-ray neutrons: 14C atoms react with O2 to form CO2 • CO2 then is incorporated into plant life by photosynthesis. After material dies 14C content decreases from radioactive decay • 14C half-life is 5730 years. Radioactive Dating

  33. Uranium-lead is one of the oldest and most refined of the radiometric dating schemes, with a dating range of about 1 million years to over 4.5 billion years. • The method relies on two separate decay chains, the Uranium series, from 238U to 206Pb, with a half-life of 4.47 billion years and the actinium series from 235U to 207Pb, with a half-life of 704 million years. These decay routes occur via a series of alpha (and beta) decays. The uranium-lead and potassium-argon methods are used for dating older objects.

  34. Potassium-Argon dating is a viable technique for dating very old archaeological materials. Geologists use this method to date rocks as much as 4 billion years old. It is based on the fact that some of the radioactive isotope of Potassium, K-40, decays to the gas Argon as Ar-40.    • Potassium is one of the most abundant elements in the Earth's crust, 2.4% by mass. One out of every 10,000 Potassium atoms is radioactive Potassium-40. These each have 19 protons and 21 neutrons in their nucleus. If one of these protons is hit by a beta particle, it can be converted into a neutron. With 18 protons and 22 neutrons, the atom has become Argon-40, an inert gas.

  35. t1/2 = half-life k = decay constant a = 1, a is always 1 for radioactive decay Ao = initial activity t = time A = activity (disintegrations per gram) t1/2 = 0.693 k = 0.693 ak at1/2 lnAo = akt or lnA = -akt A Ao Ao = e^aktor A = e^-akt A Ao Half-life equations

  36. Ex. 3) What is k for 60Co? How much 60Co remains 15.0 years after it is initially made? 60Co has a half-life of 5.27 years. Example Problems

  37. Ex. 4) Estimate the age of an object whose 14C activity is only 55% that of living wood. The half-live of carbon-14 is 5730 years.

  38. Detection methods available depend on the fact that particles and radiations emitted by radioactive decay are energetic and some carry charges ______________ Radioactivity affects photographic plates or film as does ordinary light. ______________ contain air saturated with a vapor, the particles emitted in radioactive decay ionize air molecules in the chamber and then the vapor subsequently condenses on these ions. Photographing the ion tracks can let you study their nature in detail Detection of Radiation

  39. ions produced by ionizing radiation passing between high voltage electrodes cause a current to flow between the electrodes and then the current is amplified. Gas Ionization Counters Ex. Geiger-Mueller counter

  40. Fluorescent substances absorb energy from high energy rays and then emit the energy through visible light. Fluorescence Detection Ex. Scintillation counter

  41. Naturally occurring _______ • K-40, Thorium, Radium • Cosmic • Radiation in _______ products • Fiestaware (1936 – 1959) used U (1959 – 1973) used depleted U • Fire Detectors Uses Americium-95 • Antique Clocks and watches Used Radium which glows in the dark 1917 – women who worked at the U.S. Radium Factory were told that the Ra was harmless. They ingested deadly amounts of Ra and in turn became incredibly ill. This is an important time in history for labor rights Radiation all around us

  42. Stars are enormous thermonuclear fusion reactors generating enormous amounts of heat and energy. What keeps stars from blowing themselves apart and how do they remain stable for millions and billions of years? • How are thermonuclear reactors designed so that the hot plasma that’s around 10 million degrees does not touch the sides of the reactor and melt it? Extra problems

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