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Nuclear Chemistry - 3

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Nuclear Chemistry - 3

  1. 1. Nuclear Chemistry – Day 3Nuclear Chemistry – Day 3  Welcome! Please pick up the practiceWelcome! Please pick up the practice questions on half-lives. We will completequestions on half-lives. We will complete this prior to the quiz.this prior to the quiz.  Turn in your honors intent letter today.Turn in your honors intent letter today. Hmwk: Read Chapter 9 Section 2 and 3Hmwk: Read Chapter 9 Section 2 and 3 Test next Monday/TuesdayTest next Monday/Tuesday Notebook check next timeNotebook check next time Honors Proposal due next week.Honors Proposal due next week.
  2. 2. Warm-UpWarm-Up  Complete the half-lives and radioactiveComplete the half-lives and radioactive decay practice questions.decay practice questions.
  3. 3. AgendaAgenda  AnnouncementsAnnouncements  Warm-Up: Practice QuestionsWarm-Up: Practice Questions  Quiz – Half-lives & Radioactive DecayQuiz – Half-lives & Radioactive Decay  Notes: Fission/FusionNotes: Fission/Fusion  Video: Nuclear EnergyVideo: Nuclear Energy
  4. 4. Nuclear ForcesNuclear Forces  Protons and neutrons are tightly packed in theProtons and neutrons are tightly packed in the nucleusnucleus  Unstable nuclei undergo decay by emittingUnstable nuclei undergo decay by emitting nuclear radiationnuclear radiation  An element can have both stable and unstableAn element can have both stable and unstable isotopesisotopes  The stability of a nucleus depends on theThe stability of a nucleus depends on the nuclear forces that hold the nucleus together:nuclear forces that hold the nucleus together: these forces act between the protons and thethese forces act between the protons and the neutrons.neutrons.
  5. 5. Why don’t the positively chargedWhy don’t the positively charged protons repel each other ?protons repel each other ?  Strong nuclear forceStrong nuclear force: causes protons: causes protons and neutrons to attract each other.and neutrons to attract each other.  This attraction is much stronger than theThis attraction is much stronger than the electric repulsion between protonselectric repulsion between protons
  6. 6. Too many neutrons or protons canToo many neutrons or protons can cause a nucleus to becomecause a nucleus to become unstable and decayunstable and decay  Nuclei with more than 83 protons areNuclei with more than 83 protons are always unstablealways unstable  These nuclei will always decay – releasingThese nuclei will always decay – releasing large amounts of energy and nuclearlarge amounts of energy and nuclear radiation.radiation.  The decay results in a more stableThe decay results in a more stable nucleus.nucleus.
  7. 7. Nuclear FissionNuclear Fission  Fission: The process of splitting heavierFission: The process of splitting heavier nuclei into lighter nuclei; the process bynuclei into lighter nuclei; the process by which a nucleus splits into two or morewhich a nucleus splits into two or more fragments and releases neutrons andfragments and releases neutrons and energyenergy
  8. 8. Nuclear Fission – Video Clip Nuclear Weapons: In fission weapons, a mass of ( enriched uranium or plutonium) is assembled into a supercritical mass —the amount of material needed to start an exponentially growing nuclear chain reaction—either by shooting one piece of subcritical material into another, or by compressing a subcritical mass with chemical explosives, at which point neutrons are injected and the reaction begins. Nuclear Power Plants: Nuclear energy is produced when a fissile material, such as uranium-235 (235U), is concentrated such that nuclear fission takes place in a controlled chain reaction and creates heat — which is used to boil water, produce steam, and drive a steam turbine. The turbine can be
  9. 9. Nuclear FusionNuclear Fusion  Fusion: the process in which light nucleiFusion: the process in which light nuclei combine at extremely high temperatures,combine at extremely high temperatures, forming heavier nuclei and releasingforming heavier nuclei and releasing energyenergy
  10. 10. How the Sun shines Nuclear fusion is the energy source of stars – just like our own Sun. It has a nuclear fusion reactor at its core. The immense pressure and a temperature of 16 million degrees C force atomic nuclei to fuse and liberate energy. About four million tons of matter is converted into sunlight every second.
  11. 11. Nuclear Radiation TodayNuclear Radiation Today  Nuclear radiation is all around you.Nuclear radiation is all around you. Background radiationBackground radiation is the nuclearis the nuclear radiation that arises naturally from cosmicradiation that arises naturally from cosmic rays and from radioactive isotopes in therays and from radioactive isotopes in the soil and air.soil and air.  Radiation is measured in units of rems.Radiation is measured in units of rems.  Exposure varies depending on locationExposure varies depending on location and activities.and activities.
  12. 12. Beneficial Uses of NuclearBeneficial Uses of Nuclear RadiationRadiation  Smoke detectors – a small alpha-emittingSmoke detectors – a small alpha-emitting isotope is used to detect smoke particlesisotope is used to detect smoke particles in the air.in the air.  Disease detection – radioactive tracersDisease detection – radioactive tracers are added to a substance so that itsare added to a substance so that its distribution can be detected later. Thesedistribution can be detected later. These are widely used in medicine.are widely used in medicine.  D:Ch0975459.htmlD:Ch0975459.html tracer cliptracer clip
  13. 13. Benefits continuedBenefits continued  Nuclear radiation therapy is used to treatNuclear radiation therapy is used to treat cancer.cancer.  Agriculture - radioactive tracers and radio-Agriculture - radioactive tracers and radio- isotopes are used to help scientistsisotopes are used to help scientists understand biological processes in plants.understand biological processes in plants.
  14. 14. MRI image of a healthy brainMRI image of a healthy brain
  15. 15. MRI image of a brain withMRI image of a brain with Alzheimer’s DiseaseAlzheimer’s Disease
  16. 16. Possible Risks of Nuclear RadiationPossible Risks of Nuclear Radiation  Nuclear radiation can ionize atomsNuclear radiation can ionize atoms Ionization is a change in the number ofIonization is a change in the number of electrons in an atom or molecule, causing theelectrons in an atom or molecule, causing the particle to be positively or negatively charged.particle to be positively or negatively charged.  Radiation sickness results from high levelsRadiation sickness results from high levels of nuclear radiationof nuclear radiation Studies have shown a relationship betweenStudies have shown a relationship between high levels of radiation exposure and cancer.high levels of radiation exposure and cancer. (Risk is determined by amount of exposure)(Risk is determined by amount of exposure)
  17. 17. Nuclear PowerNuclear Power  Nuclear fission is an alternative to fossilNuclear fission is an alternative to fossil fuels as a source of energy.fuels as a source of energy.  Radioactive products of fission must beRadioactive products of fission must be handled carefully and nuclear waste musthandled carefully and nuclear waste must be safely stored.be safely stored.  Scientists are working on nuclear fusionScientists are working on nuclear fusion reactors, but fusion reactions are difficultreactors, but fusion reactions are difficult to produce in the laboratory.to produce in the laboratory.

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