Transcript Document
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; These reactions involve the protons and neutrons in the nucleus There are two types of nuclear reaction Fission and Fusion Reactions 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. Fusion Reactions • These involve nucleii joining together to make larger ones. • These type of reactions are what go on inside stars and provide the energy which make them shine. 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 ionises atoms it bumps into 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 An decay reaction The Uranium atom U23892 decays by particle emission 238 U 92 He What is represented by ? 4 2 + ? 234 90 An decay reaction The Uranium atom U23892 decays by particle emission 238 U 92 He 4 2 234 + Th 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. More decay reactions The Thorium atom Th22790 decays by particle emission 227 Th 90 Complete the equation More decay reactions 227 Th 90 He 4 2 223 + Ra 88 More decay reactions The Actinium atom Ac22589 decays by 3 particle emissions 225 Ac 89 Complete the equation More decay reactions 225 Ac 89 3He 4 2 213 + Bi 83 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 becomes a proton. N10 p11 0-1 Particle emissions The effect of Particle emission is to increase the proton count by 1 whilst leaving the overall mass unchanged. 231 Th 90 What is ? 0 -1 + ? Particle emissions The effect of Particle emission is to increase the proton count by 1 whilst leaving the overall mass unchanged. 231 Th 90 231 0 -1 + Pa 91 Notice how particle emission raises the atomic number by 1 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 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. 240 * U23892 Mass 200 78 Number 93 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 240 * U23892 Th23490 * Mass 200 78 Number 93 Plotting a beta emission • The Thorium next loses a Beta particle • Work out what would be formed • Add the nucleus onto your chart 240 * U23892 Th23490 * * Pa23491 Mass 200 78 Number 93 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 ! Emission sequence (including the first two example emissions) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.