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Nuclear Processes

Nuclear Processes. In chemical reactions, electrons in atoms are responsible for bonds forming and being destroyed. The identity of the atoms involved does not change. This is not true for nuclear processes because; .

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Nuclear Processes

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  1. Nuclear Processes

  2. In chemical reactions, electrons in atoms are responsible for bonds forming and being destroyed. The identity of the atoms involved does not change

  3. This is not true for nuclear processes because; These reactions involve the protons and neutrons in the nucleus – too large or too small of a ratio between protons and neutrons

  4. There are two types of nuclear reaction Fission and Fusion Reactions

  5. Fission Reactions • Involve a nucleus collapsing to form a smaller nucleus • Usually involve atoms with large nucleii such as the Lathanides and Actinides • They produce ,  and  emissions.

  6. Fusion Reactions • These involve nuclei joining together to make larger ones. • These type of reactions are what go on inside stars and provide the energy that causes them to shine.

  7. The  particle • Consists of 2 protons and 2 neutrons • Is emitted from a nucleus during radio active decay • Is the most destructive radiation because it ionizes atoms it bumps into

  8. The  particle • Has a relative mass of 4 amu • Low penetration ability (stopped by paper or skin) • Harmful if ingested or inhaled (can’t get out) • Decreases atomic number by 2 • Decreases mass by 4

  9. The  particle • The particle is the same as a Helium atom with the electrons removed. • It is often written as He 42 in nuclear equations

  10. An  decay reaction The Uranium atom U23892 decays by  particle emission 238 4 234 U He ? + 2 92 90 What is represented by ?

  11. An  decay reaction The Uranium atom U23892 decays by  particle emission 238 4 234 U He Th + 2 92 90 Th is thorium – we can work it out by using the periodic table and looking up the atom with atomic number 90. The mass number does not matter – it is simply an isotope of Th.

  12. More  decay reactions The Thorium atom Th22790 decays by  particle emission 227 Th Complete the equation 90

  13. More  decay reactions 227 4 223 Th He Ra + 2 90 88

  14. More  decay reactions The Actinium atom Ac22589 decays by 3  particle emissions 225 Ac Complete the equation 89

  15. More  decay reactions 225 4 213 Ac 3He Bi + 2 89 83

  16.  Particle emissions  Particles are electrons but they do not come from the electron shells which surround the nucleus – they come from the nucleus itself. The electron is emitted when a neutron sheds its negative charge and becomes a proton. N10p110-1

  17. Tritium decay (beta)

  18.  Particle emissions The effect of  Particle emission is to increase the proton count by 1 whilst leaving the overall mass unchanged. 231 231 0 Th  ? Pa + -1 90 91 What is ?

  19. Decay Series When a radioactive nucleus such as U23892 decays it often produces another radioactive isotope which goes on to decay further. We are going to construct a decay series on graph paper for the element U23892 to show how it eventually forms a stable isotope of lead Pb20682

  20. GET A PIECE OF GRAPH PAPER • Draw a vertical axis representing atomic mass. It will need to run from 200 to 240 • Draw a horizontal axis representing atomic number. It will need to run from 78 to 93. • Position the isotope U23892 on your graph and mark it clearly.

  21. 240 * U23892 Mass 200 78 93 Number

  22. Plotting an  decay • The nucleus gives off an alpha particle first to form a new nucleus • Work out what the new nucleus is • Find the nucleus on your graph and add it in • Join the points with an arrow

  23. 240 * U23892 Th23490 * Mass 200 78 93 Number

  24. Plotting a beta emission • The Thorium next loses a Beta particle • Work out what would be formed • Add the nucleus onto your chart

  25. 240 * U23892 Th23490 * * Pa23491 Mass 200 78 93 Number

  26. Building up the decay series Continue to build up the series using the following emissions. Each alpha emission is shown as a diagonal to the left and each beta emission is a horizontal line to the right. If you are successful you should end up with Pb20682 Good Luck !

  27.       8.  9.  10.  11.  12.  13.  14.  Emission sequence (including the first two example emissions)

  28. Electron Capture • Some times a nucleus will capture an electron and a proton converts to a neutron. • This decreases the atomic number but does not change the mass • 201Hg80 + 0-1e  201Au79 + γ00

  29. Positron Emission • A positron has the mass of an electron and the charge of a proton – it’s kind of like a “positive electron” • It may be emitted when a proton turns into a neutron • Atomic number decreases and mass stays the same. • 22Na11 0+1e + 22Ne10

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