Atomic Science
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The document discusses atomic science and radioactive decay. It introduces key concepts like alpha decay, beta decay, gamma decay, and the factors that influence nuclear stability. Students are given various assessment tasks to help them learn concepts like drawing atomic models, defining atomic terminology, investigating isotopes, and exploring the forces that hold the nucleus together or cause it to decay.
Atomic Science
- 1. Atomic Science Introductory Physics/ Environmental Science Canadian Academy Alpha decay image from h3p://en.wikipedia.org/wiki/Alpha_decay
- 2. Atomic Science Unit Ques?ons: “?” Enduring Understandings: • Nuclear energy can be used to generate electricity Areas of interac9on: Human Ingenuity The development of electrical technologies revolu6onised culture Environments Can we maximise efficiency in order to maximise sustainability? Criterion Assessment Tasks C: Unit Test E: Half-‐life inves?ga?on A & B: One World
- 3. Draw an Atom! What are the names, sizes, charges and posi?ons of the components? What is the relevance of this to radioac?vity?
- 4. The Ob-‐Scertainer How can we really know what we cannot see? Science is a process of observa?ons, hypotheses and tes?ng. 1. Take 4 or 5 ob-‐scertainers. Play a bit. Predict the shape inside. 2. Test your hypothesis with careful movements and observa?ons. 3. Draw your ‘final’ structure. Conclude. Play, predict, draw Modify, conclude Test 4. Have an ob-‐scertainer class conference and come up consensus on the best structure of each of the dishes (there are 12 in total).
- 6. Atomic Terminology Define these terms and then arrange them into a mind-‐map or diagram. Atom Nuclide Nucleus & Nucleons Atomic Number (Z) Mass Number (A) Neutrons (N) Isotope
- 7. Atomic Terminology Define these terms and then arrange them into a mind-‐map or diagram. Atom: ‘un-‐cu3able’ – the smallest unit of an element Nuclide: an atom specified by an atomic and mass number Nucleus & Nucleons – protons (+) and neutrons (0) in a nucleus Atomic Number (Z) – number of protons in the nucleus, defines the element atomZahl Mass Number (A) – number of nucleons. Defines the isotope. Neutrons (N) = mass number – atomic number Isotope = atoms of the same element with different mass numbers.
- 8. Protons vs Neutrons Work through the periodic table and plot every figh element. What trends and pa=erns can you iden?fy? Can you suggest a reason for this? Mass Number (A) Mass Number (A) 12 Atomic Number (Z) 6 C Neutrons (N) = mass number – atomic number Atomic Number (Z) 8 Grid from Desmos the online graphical calculator h3ps://www.abe3ercalculator.com/c
- 9. Radioac9ve Stability Think about all those posi?vely-‐charged protons next to each other. What do they want to do? What happens if you add more protons? Alpha decay image from h3p://en.wikipedia.org/wiki/Alpha_decay
- 10. Radioac9ve Stability Think about all those posi?vely-‐charged protons next to each other. What do they want to do? What happens if you add more protons? This repulsive force is the electromagne9c force. It is not par?cularly strong, but acts over a large distance. So how does the nucleus stay together? electromagne?c force Alpha decay image from h3p://en.wikipedia.org/wiki/Alpha_decay
- 11. Radioac9ve Stability Think about all those posi?vely-‐charged protons next to each other. What do they want to do? What happens if you add more protons? This repulsive force is the electromagne9c force. It is not par?cularly strong, but acts over a large distance. So how does the nucleus stay together? electromagne?c force The strong force acts between neutrons and protons. It s?cks them together (using gluons – yes, really). The strong force is strong, but acts only strong force over a ?ny distance. As the size of the atom increases, more neutrons are required to keep it stable. Alpha decay image from h3p://en.wikipedia.org/wiki/Alpha_decay
- 12. Radioac9ve Decay When the forces inside the nucleus are unbalanced, decay occurs. What condi?ons favour these different forms of radioac?ve decay? h3p://phet.colorado.edu/en/simula?on/alpha-‐decay -‐ -‐ Gamma decay ( ) is high-‐frequency energy which accompanies other forms of decay. h3p://phet.colorado.edu/en/simula?on/beta-‐decay Alpha decay image from h3p://en.wikipedia.org/wiki/Alpha_decay
- 13. Radioac9ve Decay Radioac?ve decay is a natural, random change in atomic nuclei that goes on all around us. Radioac?ve materials are going through radioac?ve decay. In this group task, find out about one type of decay and explain to others. Alpha decay symbol: ( ) Beta-‐ decay symbol: ( ) Gamma Decay symbol: ( γ ) Nucleus is too large and Nucleus has too many… Nucleus has too much posi?ve. energy ager α or β decay. ___________ is released _________ and _______ are A gamma ray is released from the nucleus. released from the nucleus. from the nucleus. The alpha par?cle is a stable The beta-‐par?cle is a fast-‐ The gamma ray is a photon ___________ nucleus (__ moving… of high-‐frequency energy. protons and ___ neutrons) Diagram: Diagram: Penetra?ng ability: Penetra?ng ability: Penetra?ng ability: Will pass through thin lead. Image from: h3p://en.wikipedia.org/wiki/Gamma_decay#Gamma_ray_produc?on
- 14. Radia9on Radioac?ve decay emits radia?on in different forms. Radia?on is considered harmful if it is ionizing. This means it interacts with electrons in living things, causing them to become ionised. This results in free radical forma?on, and lots of damage to cells and ?ssues. When damage is caused to DNA, this can lead to cancers. Although α radia?on is easily stopped, it may be dangerous if inhaled or ingested. par?cles energy Penetra?on image from h3p://en.wikipedia.org/wiki/Radia?on
- 15. Decay Equa9ons Decay (proton: neutron ra?o too high) An par?cle (He) is always lost. Mass number decreases by 4. Atomic number decreases by 2. 235 4 ? 92 U! 2 He + ? X 4 He 2 40 4 ? 19 K! 2 He + ? X 209 205 ? 84 Po ! 82 Pb + ? ? Some gamma energy is released, but is not a par6cle (so does figure in our equa6ons) Alpha decay image from h3p://en.wikipedia.org/wiki/Alpha_decay
- 16. Decay Equa9ons -‐ Decay (too many neutrons) -‐ Decay (too many neutrons) A neutron decays into: Neutron decays into proton. • Proton (remains in nucleus) Electron and an?neutrino released. • -‐ par?cle (fast electron) • An?neutrino Some gamma energy is released, but is not a par6cle (so does figure in our equa6ons) Alpha decay image from h3p://en.wikipedia.org/wiki/Beta_decay
- 17. Decay Equa9ons Decay (proton: neutron ra?o too high) -‐ Decay (too many neutrons) An par?cle (He) is always lost. Neutron decays into proton. Electron and an?neutrino released. 235 4 231 92 U! 2 He + 90 Th 40 4 36 19 K! 2 He + 17 Cl 209 205 4 plus Decay (too many protons) 84 Po ! 82 Pb + He 2 Proton decays into neutron. Posi?ve electron (positron)and neutrino released.
- 18. Radioac9ve Decay of Uranium 238 It takes billions of years and many cycles of decay and -‐ decay for radioac9ve 238U to become stable 206Pb. Work through the puzzle on the sheet, prac?cing the decay equa?ons and proper nota?on of the isotopes as you go. If you finish: Find out more about ‘half life’. What does it mean?
- 19. Decay Lab Carry out this inves6ga6on to learn more about half-‐lives. Assessed for Criterion E: Processing Data. 100 Green beads 100 White beads Radioac?ve green beads decay into white beads. This process is random. Record the start ?me. Remove 4 greens from the cup and put in ‘discard’. 2. replace extra Replace with white 4 daughter beads. daughters Record “4” as the number of greens removed. Cover, shake and select 4 at random again. white Count and record the greens. Discard and replace. 1. random 4 sample green Repeat un?l 20 random samples have been taken. Record the number of greens each ?me. discard Record the finish ?me. Total ?me/20 = mean ?me per sample. Record. How could you graph these data Reset the simula9on and repeat, and use them to calculate the half this 9me taking 8 beads at random per sample. life of the green beads?
- 20. Decay Lab Carry out this inves6ga6on to learn more about half-‐lives. Assessed for Criterion E: Processing Data. 100 Green beads 100 White beads Decreasing Increasing 2. replace extra daughters white 1. random 4 sample green discard Total 6me for each experiment When you have finished the sampling, save and 20 cycles of random sampling – 4 at a 9me. send to your partner. You’re on your own now. Then: Go to Tools – Protec6on –Unprotect Sheet to be able to complete the rest of the task. Reset the simula9on and repeat, this 9me taking 8 beads at random per sample.
- 21. Decay Lab Carry out this inves6ga6on to learn more about half-‐lives. Assessed for Criterion E: Processing Data. Plot best-‐fit decay curves (no need for the increases). Adjust the polynomial order so the curves are smooth and realis?c. Remove the labels for the curves which will appear in this legend.
- 22. Decay Lab Carry out this inves6ga6on to learn more about half-‐lives. Assessed for Criterion E: Processing Data. Calcula9ng Half Life For each curve, find as many ‘half intervals’ as possible (e.g. 100-‐>50, 80-‐>40, 60-‐>30). Take a mean of these half intervals. This is an es?mate of the half-‐life of the isotope. What differences do you find between the 4-‐sample and the 8-‐sample? Which es?mate of half life is more reliable? Why? Plot best-‐fit decay curves (no need for the increases). Adjust the polynomial order so the curves are smooth and realis?c. Remove the labels for the curves which will appear in this legend.
- 23. Decay Lab Carry out this inves6ga6on to learn more about half-‐lives. Assessed for Criterion E: Processing Data. Plot best-‐fit decay curves (no need for the increases). Adjust the polynomial order so the curves are smooth and realis?c. Remove the labels for the curves which will appear in this legend.
- 24. Decay Lab Carry out this inves6ga6on to learn more about half-‐lives. Assessed for Criterion E: Processing Data. In the conclusion, work through this scenario. Assume that in the 4-‐sample test, 1 minute represents 100 years. For the material to be considered ‘safe’, it needs to decay to 1/16 of its original amount. Answer the following ques9ons, with jus9fica9on. • How long do you need to be concerned about the material? • How might you store it safely for that long?
- 25. Decay occurs at random – we can’t predict when an individual Half Life atoms will decay. However, we can predict the rate at which large quan??es will decay, and this is called half-‐life. “The radioac6ve half-‐life for a given radioisotope is the 6me for half the radioac6ve nuclei in any sample to undergo radioac6ve decay.” Hyperphysics (h=p://hyperphysics.phy-‐astr.gsu.edu/hbase/nuclear/halfli.html) Use this PhET Lab to find out more about half lives of 13C and 238U and how they can be used to es?mate the age of geological materials. Cool. h3p://phet.colorado.edu/en/simula?on/radioac?ve-‐da?ng-‐game
- 26. Biological Effects of Radia9on Ionising radia?on can damage living ?ssues by causing atoms to become ions, which can in turn become damaging free-‐radicals. Infographic from: h3p://www.theglobeandmail.com/news/world/asia-‐pacific/how-‐ radia?on-‐affects-‐the-‐body/ar?cle1942117/?from=1942081
- 27. Biological Effects of Radia9on Infographic from: h3p://www.theglobeandmail.com/news/world/asia-‐pacific/how-‐ radia?on-‐affects-‐the-‐body/ar?cle1942117/?from=1942081
- 28. Uses of Nuclear Radia9on Find out more about these uses of radia?on: • What type of radia?on? • How is it used? da?ng Rad iocarbon Sterilising fo od & medical e quipment Radioac?ve tracers & diagnosis Radiotherapy: cancer treatment Smoke detec tors
- 29. Some Decays. Which are α and which are β-‐? 238 4 234 218 4 214 92 U! 2 He + 90Th 84 Po ! 2 He + 82 Pb 214 0 214 234 90 Th ! 0 "1 e+ 234 91 Pa +! 82 Pb ! "1 e+ 83 Bi +! 214 0 214 234 91 Pa ! 0 "1 e+ 234 92 U +! 83 Bi ! "1 e+ 84 Po +! 234 4 230 214 4 210 92 U! 2 He + 90Th 84 Po ! 2 He + 82 Pb 210 0 210 230 Th ! 4 He + 226 Ra 82 Pb ! "1 e+ 83 Bi +! 90 2 88 210 0 210 226 4 222 83 Bi ! "1 e+ 84 Po +! 88 Ra ! 2 He + 86 Rn 210 4 206 222 4 218 84 Po ! 2 He + 82 Pb 86 Rn ! 2 He + 84 Po 29
- 30. Which is the correct α decay equa?on? Which is the correct β-‐ decay equa?on? A. B. 238 4 234 214 0 214 92 U! 2 He + 90 Th 82 Pb ! +1 e+ 83 Bi +! C. D. 234 0 234 214 1 213 91 Pa ! "1 e+ 92 U +! 84 Po ! H + 1 83 Bi Which product is correct? A. 222 B. 222 87 Fr 86 Rn 226 4 ? 88 Ra ! 2 He + ? ? C. 225 223 D. 80 U 86 Rn Which product is correct? A. 222 B. 222 234 0 ? 87 Fr 86 Rn 90 Th ! "1 e+ ? ? +! C. 238 234 D. 92 U 91 Pa
- 31. Which product is correct? A. 17 B. 18 9 F 9 F 17 4 ? 8 O! 2 He + ? ? C. 13 D. 13 C 6 C 7 Which product is correct? A. 211 B. 210 210 0 ? 83 Bi 83 Bi 82 Pb ! "1 e + ? +! ? C. 206 D. 214 80 Hg 84 Po Which product is correct? A. 220 B. 210 84 Po 83 Bi ? 4 235 ? ?! 2 He + U 92 C. 206 D. 239 80 Hg 94 Pu
- 32. Check the periodic table. Which are the most common isotopes? A. 14 B. 12 A. 211 B. 209 6 C 6 C 83 Bi 83 Bi C. 12 C. 209 6 C D. 13 C 7 84 Bi D. 208 83 Bi Which nuclide is correct? A. 137 B. 141 ? 0 137 55 Cs 58 La ? ?! "1 e+ 56 Ba +! C. 135 D. 131 55 Cs 53 Xe Which nuclide is correct? A. 220 B. 236 84 Po 95 Am ? 4 237 ? ?! 2 He + 93 Np C. 241 D. 233 95 Am 91 Pa
- 33. Where does our energy come from?
- 34. Where does our energy come from? Nuclear fusion reac?ons occur in the core of the Sun. How does the Sun’s energy give us the energy we use on Earth? 1. Core 5. Chromosphere 6. Corona 2. Radia?ve zone 7. Sunspot 3. Convec?ve zone 8. Granules 4. Photosphere 9. Prominence Images from:h3p://en.wikipedia.org/wiki/Sun
- 35. Nuclear Fusion is how the Sun generates energy! Iden?fy these nuclei. What happens here? What are the products? What is this? What nuclear force must be overcome in order for fusion t occur? For us to achieve this on Earth takes massive amounts of energy and resources. Fusion is not (yet) a realis?c way of genera?ng energy. Images from: h3p://en.wikipedia.org/wiki/Nuclear_fusion
- 36. Nuclear Fusion is how the Sun generates energy… … but we can’t reliably do it here on Earth. Nuclear Fission is what we mean by atomic energy. Images from: h3p://en.wikipedia.org/wiki/Nuclear_fusion
- 37. Nuclear Fission is how we generate ‘atomic energy’. Open this PhET Lab on Fission. Describe how a fission reac?on works. • What is the role of the neutron? • What happens to the 235U nuclide? • How is energy released? Switch to the Chain Reac9on Set it up in a containment vessel. • What happens when you add more 235U? • How does 238U behave? • Which isotope would you choose to sustain a chain reac?on, releasing energy? Switch to the Nuclear Reactor Set it up and get it running! • What is the effect of removing the control rods from the reactor? h3p://phet.colorado.edu/en/simula?on/nuclear-‐fission • How could control rods be used to maintain safety and control output of energy? • What are they made of?
- 38. Nuclear Fission is how we generate ‘atomic energy’. Annotate this diagram to describe what is happening in a 1 neutron in nuclear fission reac?on. This fission equa9on represents the reac?on: 235 92 U + 01n ! 3 01n + 141Ba + 36 Kr 56 92 Complete these fission equa?ons: 235 92 U + 1n ! 3 1n + 90 Rb + ? ? 0 0 37 ? energy 235 92 U + 01n ! 3 01n + 143 55 Cs + ? ? ? 3 neutrons These neutrons can go on to split other produced 235U nuclides in a chain reac6on. Image from: h3p://en.wikipedia.org/wiki/Nuclear_fission
- 39. Nuclear Energy how do we get electricity from this? It takes a lot of binding energy to hold a nucleus together. When we split the atom, we release the daughter par?cles, some neutrons and gamma radia?on. Gamma radia?on is high-‐frequency energy! This energy can be used to heat water, to drive a turbine and power a generator, just like conven?onal electrical genera?on. It all needs magnets to move in rela9on to coils! Control-‐rods are neutron-‐absorbent materials that can stop or control the rate of the chain reac?on and therefore control the temperature and safety of the reactor. Images from: h3p://en.wikipedia.org/wiki/Nuclear_fission and h3p://en.wikipedia.org/wiki/Pressurized_water_reactor
- 40. Radioac9ve Waste How do we get rid of it? The products of nuclear fission are radioac?ve but will decay to stable nuclides. 141 Complete the decay pathways for 92Kr and 141Ba. 92 36 Kr 56 Ba -‐, 1.8s ??, 18.3 min 92 141 ? ? ? ? ??, 4.5s ??-‐, 3.9 h 92 141 ? ? ? ? ??, 2.7h ??-‐, 32.5 days 92 141 ? ? ? ? ??, 3.5h Data from: h3p://periodictable.com/Isotopes/056.141/index2.p.full.dm.html
- 41. Radioac9ve Waste How do we get rid of it? The products of nuclear fission are radioac?ve but will decay to stable nuclides. 141 Because nuclear waste is radioac?ve, it needs to 92 36 Kr 56 Ba -‐, 1.8s -‐, 18.3 min be isolated un?l it has decayed to a safe level. This could be underground or in special treatment 92 141 facili?es. 37 Rb 57 La -‐, 4.5s -‐, 3.9 h 92 141 Nuclear reprocessing plants can take the spent fuel 38 Sr 58 Ce rods and extract fissionable materials, such as -‐, 2.7h -‐, 32.5 days plutonium, from them. These can be used in other reactors. 92 141 Y 39 59 Pr -‐, 3.5h Next genera?on nuclear reactors will use current 92 nuclear waste as fuel. 40 Zr Data from: h3p://periodictable.com/Isotopes/056.141/index2.p.full.dm.html
- 42. Can nuclear fission power the planet? 42
- 43. Fission, Fusion, α-‐Decay or β–Decay? 1. 235 92 U + 01n ! 3 01n + 143 Cs + 55 90 37 Rb 2 2. 1 H + 1 H ! 01n + 3 4 2 He + energy 3. 238 4 234 92 U! 2 He + 90 Th 4. 214 0 214 82 Pb ! "1 e+ 83 Bi +! 235 5. 92 U + 01n ! 3 01n + 141 56 Ba + 92 36 Kr 40 4 36 6. 19 K! 2 He + 17 Cl 32 0 32 15 P! "1 e+ 16 S +! 214 0 214 131 0 131 7. 83 Bi ! "1 e+ 84 Po +! 53 I! "1 e+ 54 Xe +! 43
- 44. What do you think? Ideas based on Concept Cartoons: h3p://www.conceptcartoons.com Clipart people from: h3p://www.clker.com/search/krug/1
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