1 / 36

Unit 4: Applications of Nuclear Chemistry

Unit 4: Applications of Nuclear Chemistry. Including Changes in the Nucleus. Changes in the Nucleus. Nuclear Reaction - rxn that affects the nucleus of an atom. Changes the composition of an atom’s nucleus 3 kind of radiation: Alpha particles 2+ charge Beta particles 1- charge

kineks
Download Presentation

Unit 4: Applications of Nuclear Chemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Unit 4:Applications of Nuclear Chemistry Including Changes in the Nucleus

  2. Changes in the Nucleus • Nuclear Reaction- rxn that affects the nucleus of an atom. • Changes the composition of an atom’s nucleus • 3 kind of radiation: • Alpha particles 2+ charge • Beta particles 1- charge • Gamma rays have no charge • Radioactivity- the spontaneous emission of radiation from an atom’s nucleus.

  3. Nuclear Stability • If: protons have a positive charge, nucleus is made of protons and neutrons, like charges repel; how does a nucleus stay together? • Strong Nuclear Force- an attractive force STRONGER than the electric repulsion force btwn protons. Only exists btwn particles (protons) extremely close together. • The presence of neutrons adds a net attractive force in the nucleus

  4. Types of Radioactive Decay α 42He • Alpha radiation- has 2 protons and 2 neutrons (same as a helium-4 nucleus). • Do not have much penetrating power, can be stopped by paper or skin. Does not pose a health problem.

  5. β • Beta particle- mass=0 but has a charge -1. Essentially an electron. • Can penetrate paper and skin. Does present a health hazard.

  6. γ • Gamma rays- extremely high energy ray or light. • High penetrating power. Very dangerous and hazardous to your health.

  7. Radioactive Decay • Radioactive Decay- when an atom emits any type of radiation. • Results in a new nucleus. The original nucleus decays (breaks apart) to form a new, smaller/lighter nucleus.

  8. Nuclear Equation- rxn that affects the nucleus of an atom. “In any radioactive decay, the sum of the mass #s and the atomic #s are the same before and after the reaction.” (on both sides of the arrow)

  9. Try solving:

  10. Applications of Nuclear Chemistry Radioisotopes • Radioisotopes- an isotope of an element which is unstable (radioactive).

  11. Half-Life • All radioactive isotopes decay at different rates. • Half-Life- t½ , is the time required for half the atoms of a radioactive nuclide to decay. • More stable nuclides decay slowly. Less stable nuclides have shorter half-lives and decay much more quickly.

  12. Half-life practice problems • Solve: • Nitrogen-13 has a half-life of 10 minutes. IF there are 2.00g of nitrogen-13 at the start, how many grams will exist after 3 half-lives? • How long will it take 3.8 x 1024 atoms of 10047Ag to disintegrate to 2.93 x 1023 atoms if the half life of  10047Ag is 24.6 seconds? • Radioactive copper, 6429Cu, is found in quantities exceeding pollution standards in the  sediments of a reservoir in a routine check on Monday.  The standard allows up to 14 ppm/cubic meter of sediment.  On Monday, 59ppm/cubic meter were measured. The half life of 6429Cu is 12.7 hours.  When will the pollution level return to 14ppm?

  13. Nuclear Bombardment Reactions • We can make stable nuclei by: • Nuclear Bombardment Rxns- an atom is bombarded with a stream of particles like alpha particles. • When the nucleus is hit, the particles and the nucleus combine to form a new, unstable, nucleus.

  14. Atom Smashing! Fermi National Accelerator Laboratory, Illinois cyclotron

  15. Stanford Linear Accelerator Center, California.

  16. Can also bombard with neutrons… • 1934, Enrico Fermi figured out that we can make radioactive isotopes by smashing nuclei with neutrons.

  17. Biological Effects of Radiation • Units of Radiation: • SI unit: becquerel (Bq) • more common: the curie (Ci)- only measures amount of radiation • Most often used: the rem(roentgen equivalent for man) – measures amount of radiation & the sensitivity of the body • < 150 rem: not fatal but can cause serious damage • 150 – 1000 rem: Damaging and can be fatal • > 1000 rem: FATAL!

  18. Measuring Doses & Detecting Radiation Dose Amount Radiation Amount Geiger Counter: most common instrument used for detecting radiation. As radiation passes through it’s window, it ionizes gas in the cylinder. Ions strike a charged cylinder and wire which created an electric pulse…. Which clicks and is read on the counter. • Dosimeter: small badge or pen warn on the person. • Like a mini Geiger counter. • Used to monitor personal radiation exposure. • The film is developed after use, the darker the film the more exposure experienced.

  19. Beneficial Uses of Radioisotopes • Radiotracers: used to follow a specific substance as it moves through a natural system. Ex- your body. • Cancer treatment: Fast growing cancer cells are more susceptible to radiation than healthy cells. The hope is, cancer cells will be damaged and die while healthy cells survive treatment. • Food Preservation: can prevent spoiling of food.

  20. Harnessing the Nucleus:Fission vs. Fusion • Besides nuclear decay and bombardment, there are 2 other types of nuclear reactions. 1. Nuclear Fission & 2. Nuclear Fusion

  21. Nuclear Fission • Enrico Fermi bombarded uranium-238 with neutron (s) which eventually becomes Neptunium- 239 (a heavier element). • 1938 Otto Hahn & Fritz Strassman • Tried to replicate Fermi’s experiment but they also got Barium (a lighter element). • Couldn’t figure out why. Wrote letter to Meitner. • Lise Meitner • Thought that the nucleus must become unstable and BREAK APART to form the lighter atom.

  22. Nuclear fission cont. • Meitner was RIGHT! but Hahn got the Nobel prize. • Nuclear Fission- a large nucleus is split into 2 smaller nuclei of approximately equal mass.

  23. Energy & “Missing” Mass • There is so much nuclear energy in a very small amount of mass. • 4.5g of U-235 = 1 persons energy use for 1 year. • Compared to 15 tons of coal. • Where does the energy come from?- the “missing” mass is matter that has been converted into energy via Einstein’s E=MC2.

  24. Chain RXNs and The Atomic Bomb • Because, in a fission rxn, neutrons are released as the U atom breaks apart, they can go and bombard other U atoms and cause them to break apart. • Chain Reaction- a continuous series of fission rxns.

  25. The atomic bomb relies on a runaway chain rxn. http://www.youtube.com/watch?v=qT4mSoZsbzM http://www.youtube.com/watch?v=RqyBzXYZPoM

  26. Nuclear Reactors • Nuclear power plants use the fission process to heat water into steam, that drives a generator. Turning nuclear reactions into electricity.

  27. Three Mile Island, Pa • Lost water, due to operator error, and the rising heat could cause a “meltdown”. • Water was restored and a disaster was averted.

  28. Chernobyl, Russia • Used Graphite to absorb neutrons, graphite ignited and burned out of control. Burned for days, destroying the reactor and releasing huge amounts of radiation. • Winds carried the radiation into Europe… many people developed cancers, malformed children, etc.

  29. Nuclear Waste Disposal • Radioactive fission products build-up on fuel rods. Eventually the fuel rods have to be replaced. • Currently, waste stored at site. Best solution burial but no country has an underground site. • Yucca Mountain- was designed to be the U.S.’s underground storage site.

  30. Nuclear Fusion • Nuclear Fusion- 2 small nuclei join to form a large nucleus. • Releases a considerable amount of energy. • Down side- difficult to produce and hard to control! Type of nuclear rxn that takes place on the sun.

  31. The Hydrogen Bomb! • http://www.youtube.com/watch?v=NNcQX033V_M • Releases much more energy than an atomic bomb. • Triggered by a small atomic blast. • Only tested, never used in a conflict.

  32. Fusion Research • Gram for Gram, fusion rxns releases more energy than fission rxns. • Controlled fusions are difficult and require temps of 40 million K or more. (difficult!- no material can withstand that kind of temps.)

  33. Cold Fusion?? • 1989- Pons & Fleishman @ the University of Utah. • Claimed to achieve cold fusion by the electrolysis of heavy water (D2O). • Didn’t work out as claimed.

More Related