Nuclear Forces Pp


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Nuclear Forces Pp

  1. 2. Nuclear Forces <ul><li>Strong nuclear forces keep the nucleons together. These are powerful short-range force of attraction between the proton-proton, proton-neutron, and the neutron-neutron. This is distinct from the electrostatic force or gravitational force </li></ul>
  2. 3. Nuclear Mass Defect <ul><li>The difference between the mass of a nucleus and the sum of the masses of its constituent particles. The mass defect is converted into energy units by using Einstein’s equation, </li></ul><ul><li>E= mc 2 </li></ul>
  3. 4. nuclear binding energy <ul><li>The energy is usually referred to as the nuclear binding energy which is released when the nucleus is formed from its constituent particles </li></ul>
  4. 5. Comparison <ul><li>Lightest and heaviest elements have the smallest binding energies per nuclear particle. These are therefore less stable than the nuclei than the nuclei of elements having intermediate atomic weights. </li></ul>
  5. 6. Nuclear Stability <ul><li>(Refer to overhead of p. 803) </li></ul><ul><li>In low atomic number elements , nuclei with greater number of neutrons than protons have lower binding energies and are less stable. </li></ul><ul><li>The most stable have a 1:1 ratio of </li></ul><ul><li>Neutron:Proton </li></ul>
  6. 7. Higher Atomic Number <ul><li>Stable nuclei have a neutron-proton ratio increasingly greater than 1:1 </li></ul>
  7. 8. Odd-Even <ul><li>Stable – even </li></ul><ul><li>Rarely stable -- odd </li></ul>
  8. 9. Radioactive Decay <ul><li>The emission of an alpha particle, a beta particle or gamma rays and the formation of slightly lighter and more stable nucleus </li></ul>
  9. 10. Nuclear Disintegration <ul><li>A nucleus is bombarded with alpha particles, protons, deuterons, neutrons or other particles. The unstable nucleus emits a proton or a neutron and becomes more stable </li></ul>
  10. 11. Fission <ul><li>The process in which a very heavy nucleus splits to form medium- weight nuclei </li></ul>
  11. 12. Fusion <ul><li>The process in which lightweight nuclei combine to form heavier, more stable nuclei </li></ul>
  12. 13. Properties of Radioacitive Nuclides <ul><li>The affect light –sensitive emulsion on a photographic film </li></ul><ul><li>The produce an electric charge in the surrounding air(ionizing radiation) </li></ul><ul><li>The produce fluorescence with certain other compounds </li></ul><ul><li>Their radiations have special physiological effects </li></ul><ul><li>The undergo radioactive decay </li></ul>
  13. 14. Half-life <ul><li>The length of time during which half of a given number of atoms of a radioactive nuclide decays </li></ul>
  14. 15. Nature of Radiation <ul><li>Alpha particles – slow, positive. Can burn flesh and ionize air easily </li></ul><ul><li>Beta particles – fast, negative </li></ul><ul><li>Gamma Rays- high-energy electromagnetic waves. Like visible light but much shorter wavelength and higher frequency </li></ul>
  15. 16. Shielding Ability <ul><li>Compare the materials needed to shield the alpha, beta and gamma </li></ul><ul><li>Predictions?? </li></ul>
  16. 17. Result