1. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 9 Nuclear Radiation 9.6 Nuclear Fission and Fusion 1

2. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Nuclear Fission In nuclear fission, a large nucleus is bombarded with a small particle the nucleus splits into smaller nuclei and several neutrons large amounts of energy are released 2

3. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Nuclear Fission When a neutron bombards 235 U, an unstable nucleus of 236 U undergoes fission (splits) the nucleus splits to release large amounts of energy smaller nuclei are produced, such as Kr-91 and Ba-142 neutrons are also released to bombard more 235 U nuclei 3

4. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Nuclear Fission Diagram 4 1 n + 235 U 236 U 91 Kr + 142 Ba + 3 1 n + energy 0 92 92 36 56 0

5. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Nuclear Fission Chain Reaction In a nuclear chain reaction, the fission of each U-235 atom produces three neutrons that cause the nuclear fission of more and more uranium-235 atoms. 5

6. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Energy and Nuclear Fission The total mass of the products in this reaction is slightly less than the mass of the starting materials. The missing mass has been converted into energy, consistent with the famous equation derived by Albert Einstein, E = mc 2. E is the energy released, m is the mass lost, and c is the speed of light, 3.0  10 8 m/s. Using this equation, a small amount of mass is multiplied by the speed of light squared, resulting in a large amount of energy. Fission of 1 g U-235 produces same energy as 3 tons of coal. 6

7. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check Supply the missing atomic symbol to complete the equation for the following nuclear fission reaction. 1 n + 235 U 137 Te + ? X + 2 1 n + energy 0 92 52 ? 0 7

8. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution Supply the missing atomic symbol to complete the equation for the following nuclear fission reaction. 1 n + 235 U 137 Te + 97 Zr + 2 1 n + energy 0 92 52 40 0 8

9. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Nuclear Power Plants In nuclear power plants, fission is used to produce energy control rods in the reactor absorb neutrons to slow and control the chain reactions of fission 9

10. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Nuclear Fusion Fusion occurs at extremely high temperatures (100 000 000  C) combines small nuclei into larger nuclei releases large amounts of energy occurs continuously in the sun and stars 10 Hydrogen atoms combine in a fusion reactor at very high temperatures.

11. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check Indicate whether each of the following describes nuclear fission or nuclear fusion. ___ A. A nucleus splits. ___ B. Large amounts of energy are released. ___ C. Small nuclei form larger nuclei. ___ D. Hydrogen nuclei react. ___ E. Several neutrons are released. 11

12. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution Indicate whether each of the following is nuclear fission or nuclear fusion. nuclear fission A.A nucleus splits. nuclear fission and fusionB.Large amounts of energy are released. nuclear fusion C.Small nuclei form larger nuclei. nuclear fusionD.Hydrogen nuclei react. nuclear fissionE.Several neutrons are released. 12

13. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Nuclear Radiation – Concept Map 13