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CHAPTER 3.4 & 24.1 Nuclear Chemistry

CHAPTER 3.4 & 24.1 Nuclear Chemistry. Radioactivity. Radiation. Radiation : The process of emitting energy in the form of waves or particles. Where does radiation come from?

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CHAPTER 3.4 & 24.1 Nuclear Chemistry

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  1. CHAPTER3.4 & 24.1 Nuclear Chemistry Radioactivity

  2. Radiation Radiation: The process of emitting energy in the form of waves or particles. Where does radiation come from? Radiation is generally produced when particles interact or decay.A large contribution of the radiationon earth is from the sun (solar) or from radioactive isotopes of the elements (terrestrial). Radiation is going through you atthis very moment! http://www.atral.com/U238.html

  3. Man-made radiation sources that people can be exposed to include tobacco, television, medical x-rays, smoke detectors, lantern mantles, nuclear medicine, and building materials. Adding it all up, the average American is exposed to a total of about 360 millirems a year from natural and man-made radiation.

  4. Isotopes What’s an isotope? Two or more varieties of an element having the same number of protons but different number of neutrons. Certain isotopes are “unstable” and decay to lighter isotopes or elements.Deuterium and tritium are isotopes of hydrogen. In addition to the 1 proton, they have 1 and 2 additional neutrons in the nucleus respectively*. Another prime example is Uranium 238, or just 238U.

  5. Definitions • Radioactivity • emission of high-energy radiation from the nucleus of an atom • Nuclide • nucleus of an isotope

  6. Nuclear Decay • Why nuclides decay… • to obtain a stable ratio of neutrons to protons Stable Unstable (radioactive)

  7. Types of Radiation • Alpha () • helium nucleus paper 2+ • Beta-minus () • electron lead 1- • Gamma () • high-energy photon concrete 0

  8. Where do these particles come from ? • These particles generally come from the nuclei of atomic isotopeswhich are not stable. • The decay chain of Uranium produces all three of these formsof radiation. • Let’s look at them in more detail…

  9. Note: This is theatomic weight, whichis the number ofprotons plus neutrons Alpha Particles (a) Radium R226 Radon Rn222 p + n n p a (4He) 88 protons 138 neutrons 86 protons 136 neutrons 2 protons 2 neutrons The alpha-particle(a) is a Helium nucleus. It’s the same as the element Helium, with the electrons stripped off !

  10. Beta Particles (b) Carbon C14 Nitrogen N14 + e- electron (beta-particle) 6 protons 8 neutrons 7 protons 7 neutrons We see that one of the neutrons from the C14 nucleus “converted” into a proton, and an electron was ejected. The remaining nucleus contains 7p and 7n, which is a nitrogennucleus. In symbolic notation, the following process occurred: n  p + e ( + n ) And a neutrino is produced too.

  11. Gamma particles (g) In much the same way that electrons in atoms can be in an excited state, so can a nucleus. Neon Ne20 Neon Ne20 + 10 protons 10 neutrons(in excited state) 10 protons 10 neutrons(lowest energy state) gamma A gamma is a high energy light particle. It is NOT visible by your naked eye because it is not in the visible part of the EM spectrum.

  12. Gamma Rays Neon Ne20 Neon Ne20 + The gamma from nuclear decayis in the X-ray/ Gamma ray part of the EM spectrum(very energetic!)

  13. Nuclear Decay…the ones we care about TRANSMUTATION • Alpha Emission • Beta Emission

  14. Example Half-lives polonium-194 0.7 seconds lead-212 10.6 hours iodine-131 8.04 days carbon-14 5,370 years uranium-238 4.5 billion years Half-life • Half-life (t½) • time it takes for half of the nuclides in a sample to decay

  15. Half-life Problem • How much of a 20-g sample of sodium-24 would remain after decaying for 30 hours? Sodium-24 has a half-life of 15 hours. GIVEN: total time = 30 hours t1/2 = 15 hours original mass = 20 g WORK: number of half-lives = 2 20 g ÷ 2 = 10 g (1 half-life) 10 g ÷ 2 = 5 g (2 half-lives) 5 g of 24Na would remain.

  16. Fission • splitting a nucleus into two or more smaller nuclei • some mass is converted to large amounts of energy

  17. Fission • chain reaction - self-feeding reaction

  18. Nuclear Weapons

  19. Cooling Tower Nuclear Power • Fission Reactors

  20. Nuclear Power • Fission Reactors

  21. Nuclear Power • Chernobyl

  22. Nuclear power • Three mile Island

  23. Fusion • combining of two nuclei to form one nucleus of larger mass • produces even more energy than fission • occurs naturally in stars

  24. Nuclear Power • Fusion Reactors (not yet sustainable)

  25. Nuclear Power • Fusion Reactors (not yet sustainable) National Spherical Torus Experiment Tokamak Fusion Test Reactor Princeton University

  26. Nuclear Power • 235U is limited • danger of meltdown • toxic waste • thermal pollution • Hydrogen is abundant • no danger of meltdown • no toxic waste • not yet sustainable FISSION FUSION vs.

  27. Cold Fusion?

  28. Others Irradiated Food Radioactive Dating Nuclear Medicine Nuclear Weapons

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