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Nuclear notation and Binding energy Contents: Atomic notation Isotopes Whiteboard Binding Energy

Nuclear notation and Binding energy Contents: Atomic notation Isotopes Whiteboard Binding Energy AMU Making an atom Calculating binding energy Whiteboards The curve of binding energy and the strong nuclear force (or why there is a limit to the periodic table). Atomic notation. X. C.

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Nuclear notation and Binding energy Contents: Atomic notation Isotopes Whiteboard Binding Energy

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  1. Nuclear notation and Binding energy • Contents: • Atomic notation • Isotopes • Whiteboard • Binding Energy • AMU • Making an atom • Calculating binding energy • Whiteboards • The curve of binding energy and the strong nuclear force (or why there is a limit to the periodic table)

  2. Atomic notation X C A 12 Z 6 • X = Symbol (C, Au) • A = Atomic Mass Number = #nucleons • (Protons + Neutrons) • Z = Atomic Number = #protons Carbon A = 12, Z = 6. #neutrons? TOC

  3. Isotopes C C 12 14 6 6 Carbon 12 has 6 Neutrons Carbon 14 has 8 Neutrons Carbon 14 is an isotope of Carbon Chemically the same Nuclear-lly different (it’s unstable) TOC

  4. Whiteboards: Atomic Notation 1 | 2 | 3 | 4 | 5 TOC

  5. What is the Atomic notation for tritium? (tritium is an isotope of Hydrogen with 2 neutrons) Hydrogen has a Z = 1, A = 1 p + 2 n = 3 W 3/1 H

  6. 10 protons, 12 neutrons. What is its atomic notation? Z = 10, A = 10 + 12 = 22, element 10 is Ne W 22/10 Ne

  7. How many neutrons in U 235? (235 = A) (1) U is element 92 235 - 92 = 143 neutrons W 143

  8. How many neutrons in Pb 208? (208 = A) (1) Pb is element 82 208 - 82 = 126 neutrons W 126

  9. How many neutrons in Kr 78? (1) Kr is element 36 78 - 36 = 42 neutrons W 42

  10. Binding energy - the energy to take an atom apart Unified Mass Units: (u) C 12 (neutral atom) = 12.0000000 u (defined) 1 u = 1.6605 x 10-27 kg = 931.5 MeV Electron = .00054858 u (not useful) Proton = 1.007276 u (not useful) H (neutral atom) = 1.007825 u (very useful) Neutron = 1.008665 u (very useful) TOC

  11. Binding energy - the energy to take an atom apart H (neutral atom) = 1.007825 u (very useful) Neutron = 1.008665 u (very useful) 1 u = 931.5 MeV • To take an atom apart: • C 12 can be taken apart into: • 6 H atoms: 6(1.007825 u) (i.e. 6 p + 6 e) • 6 Neutrons: 6(1.008665 u) • Total “taken apart” mass = 6(1.007825 u) + 6(1.008665 u) • Total “taken apart” mass = 12.09894 u • Mass “defect” = 12.09894 u - 12.000000 u = .09894 u • .09894 u - Represents energy needed to take atom apart • Binding energy = (.09894 u)(931.5 MeV/u) = 92.16 MeV TOC

  12. Binding energy - the energy to take an atom apart H (neutral atom) = 1.007825 u (very useful) Neutron = 1.008665 u (very useful) 1 u = 931.5 MeV • Binding energy in general • Look neutral atom mass in Appendix F (p 1064) • Break atom into H and n • Subtract neutral atom mass from taken apart mass • Multiply mass defect by 931.5 Mev/u TOC

  13. Whiteboards: Binding Energy 1 | 2 | 3 TOC

  14. What is the binding energy for Nitrogen 13? (Z = 7) N 13 mass = 13.005738 u H = 1.007825 u Neutron = 1.008665 u 1 u = 931.5 MeV Atom mass = 13.005738 7H + 6n = 7(1.007825 u) +6(1.008665 u) = 13.106765 u Binding energy = (13.106765 - 13.005738)931.5 MeV/u = 94.11 MeV W 94.11 MeV

  15. What is the binding energy for Carbon 14? (Z = 6) C 14 mass = 14.003242 u H = 1.007825 u Neutron = 1.008665 u 1 u = 931.5 MeV Atom mass = 14.003242 6H + 8n = 6(1.007825 u) +8(1.008665 u) = 14.11627 u Binding energy = (14.11627 - 14.003242)931.5 MeV/u = 105.3 MeV Binding energy per nucleon: C 12: 92.16/12 = 7.68 MeV/nucleon C 14: 105.3/14 = 7.52 MeV/nucleon (less) W 105.3 MeV

  16. What is the binding energy for Carbon 10? (Z = 6) C 10 mass = 10.231610 u H = 1.007825 u Neutron = 1.008665 u 1 u = 931.5 MeV Atom mass = 10.231610 6H + 4n = 6(1.007825 u) +4(1.008665 u) = 10.08161 u Binding energy = (10.08161 - 10.23161)931.5 MeV/u = -139.7 MeV (Carbon 10 does not exist) W -139.7

  17. The curve of binding energy Most tightly bound Fission releases energy Fusion releases energy Binding energy per nucleon Going to more tightly bound releases energy Fission - splitting nuclei Fusion - joining nuclei TOC

  18. Nuclear Stability Coulombic force tries to tear apart nucleus Strong Nuclear force holds it together(force between nucleons) • Strong Nuclear is very short range • As nucleus gets bigger • Strong nuclear gets weaker • Coulombic gets stronger n p p p n n p Neutrons add strong force, don’t repel Trend with heavier elements At some point neutrons don’t cut it The crazy man at UMn TOC

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