1. Fission & Fusion Why so much energy???

2. Occurs in heavy or light atoms? A neutron is absorbed by the nucleus of the Uranium-235 1 0 n + 235 92 U 142 56 Ba + 91 36 Kr + 3 1 0 n Fission Reactions heavy

3. The sum of the reactants’masses, U-235 and a neutron is 236.0526 amu (235.0439 + 1.0087) The sum of the products’ masses is 235.8659 amu. (141.9164 + 90.9234 + 3(1.0087)) Calculate the mass loss So? Why is so much energy released? 0.1867 amu

4. Let’s use Einstein’s equation E=mc 2 0.1867 x 1 gram x 1 kg 1 6.022e23 10 3 g Let’s apply Einstein’s Famous Equation E = mc 2 =3.100x10 -28 kg 2.79 x 10 -11 J/atom wow! E=3.100x10 -28 (3.00x10 8 m/s) 2

5. Critical Mass: When enough material, ie. U-235, is present to allow the produced neutrons to keep striking other U-235 atoms. Subcritical: When there is not enough U-235 & the neutrons then escape. Supercritical: Too much U-235 & can’t stop the reaction!

6. Two subcritical masses of U-235 slammed together to reach 1st Atomic Bomb: Hiroshima, Japan August 6, 1945 supercritical mass Result? E = 20,000 tons of TNT = 8.368 x 10 13 J

7. Occurs on the Sun. Hydrogen fuses to create Nuclear Fusion Helium Again, there is a mass loss. 1 1 H + 1 1 H 2 1 H + 0 1 e 1 1 H + 2 1 H 3 2 He 3 2 He + 3 2 He 4 2 He +2 1 1 H 3 2 He + 1 1 H 4 2 He + 0 1 e

8. (3.0160293 + 1.00794)amu > 4.00150 amu Calculate the energy created Just looking at the final reaction: Mass loss = 0.0224693amu 0.0224693amu x 1 gram x 1 kg = 3.731 x 10 - 29 kg 1 6.022e23amu 10 3 g E = mc 2 = 3.731 x 10 -29 kg (3.00x10 8 m/s) 2 = 3.36x10 -12 J/kg

9. Fission:Heavy atoms that are unstable. Radioactive waste w/ long ½ life. One 7g U-235 pellet can fuel a US house for 1.8 months. Fusion:Light atoms that are more stable. Requires very hot temperatures. Not much radioactive waste is generated. Fission v Fusion

10. Controls chain reaction so energy is released slowly. Only purpose is to create steam! Nuclear Reactors

11. Radon is not harmful but, it’s daughter atoms are dangerous. Radon 222 86 Rn 218 84 Po + 4 2 He When inhaled, the polonium continues to decay in lungs. Causes about 10% lung cancer.

12. Radiocarbon Dating Living things take in CO 2 Carbon’s natural isotopes are C-12 (99%) & C-14 (1%) When something dies, the C-14 continues to decay. 14 6 C 14 7 N + 0 -1 ϐ C-14 half life is 5715 years. If the ratio of C-12 to C-14 is 99.5 to.5, then how old is the artifact? 5715 years If the ratio is 99.75 to.25, then how old is it? 11,430 years.

13. Review of History of Atom Development Democritus (460-370 BC) 1st to suggest atoms are indivisible.

14. Dalton’s Atomic Theory 1.All atoms composed of tiny, particles. 2.Atoms of the same element are 3.Atoms of different elements can co combine in simple 4.Atoms are neither nor destroyed in a chemical reaction. similar. indivisible whole number ratios.

15. JJ Thomson (1896) Cathode Ray Tube Discovery? The electron.