1. TED Ed – 4 min

2. 238 92 U → 234 90 Th + 4 2 He + ɣ Write a nuclear reaction for… Uranium-238 decays into Thorium-234: 92 = 90 + 2 (conservation of atomic number) 238 = 234 + 4 (conservation of atomic mass) Uranium nucleus emits 2 protons and 2 neutrons: - an alpha particle (=helium nucleus) Don’t forget the gamma radiation!

3. 131 53 I → 131 54 Xe + 0 -1 e + ɣ Write a nuclear reaction for… Iodine-131 decays into Xenon-131: 53 = 54 – 1 (conservation of atomic number) 131 = 131 + 0 (conservation of atomic mass) Physically, what is going on here? *** a neutron changes into a proton (plus electron) *** Don’t forget the gamma radiation!

4. 14 7 N → 17 8 O + 4 2 He + Try this: splitting the atom Rutherford fired alpha particles into a jar of nitrogen gas. He discovered the products were oxygen-17 + another particle. Write the nuclear equation for the reaction: 7 + 2 = 8 + 1 (conservation of atomic number) 14 + 4 = 17 + 1 (conservation of atomic mass) 1 1 H So what actually is the other particle produced? - a hydrogen nuclei (a proton!) - no gamma (because not a decay)

5. Today’s Learning: 1)Balance equations for nuclear reactions 2)Use E=mc 2 to calculate the energy released in a nuclear reaction

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7. In Rutherford’s experiment: (printed this for you!) 14 7 N → 17 8 O + 4 2 He + 1 1 H The rest masses of the particles involved are: 1) Calculate the total mass before and after the reaction The alpha particle had an initial kinetic energy of 12.50 x 10 -13 J. After the reaction, the kinetic energy of the oxygen atom was 6.4 x 10 -14 J and the proton was 9.48 x 10 -13 J. 3) Verify Einstein’s theory of mass-energy equivalence 2) Calculate the total energy before and after the reaction

8. Check you understand and can do this yourself: Read pages 191-194 Complete and mark Activity 12A, Q1,2,3 Due…

9. Symphony of Science The Quantum World - 3min 29sec