1. NUCLEAR CHEMISTRY Unit 1

2. CHEMICAL VS. NUCLEAR - Chemical reactions Atom: involve electrons - Nuclear reactions involve the nucleus of the atom (protons & neutrons) - Nuclear reactions produce approx. 500,000 times more energy than chemical reactions NUCLEUS ELECTRONS

3. ISOTOPES AND RADIOACTIVITY - isotopes (aka: “nuclides”) are varieties of elements with different mass numbers but the same atomic number - Radioactive decay – the spontaneous emission of radiation by unstable atomic nuclei, resulting in the formation of a new atom and element - So a radioisotope is a radioactive isotope - represent an isotope like this: 2 1 H or 2 H or H-2

4. IS EVERYTHING RADIOACTIVE? - stable isotopes are nonradioactive; unstable isotopes are radioactive - ALL elements 1-82 have stable & unstable isotopes - Elements 83 and above have ONLY unstable isotopes and are radioactive. - This means they will ALWAYS decay until they reach stable configurations (so they decay to lead, #82, or smaller)

5. STABILITY Depends on: 1. Proton to Neutron ratio – a. A 1:1 ratio of protons and neutrons is stable in lighter elements Ex: C-12 is stable with 6 neutrons and 6 protons b. A 1.5:1 or 3:2 ratio is stable in heavier elements, Ex: Hg-202 is stable with 122 neutrons and 80 protons 2. Even/Odd – very generally, an even # of p and n is more stable than odd #

6. TYPES OF RADIOACTIVITY 3 kinds of radioactivity – (natural breakdown of unstable nuclei by giving off particles) 1. Alpha Particles 4 2  4 2 He - equivalent to Helium nuclei (helium without electrons) - not very penetrating (can be stopped by paper) - do not travel very fast (only 1/10 the speed of light) - very large particle (compared with others)

7. USES OF ALPHA RADIATION  Smoke Detectors!  Americium-241 releases alpha particles into the air around it, creating an electric charge. When smoke gets in the way, the charge stops and the battery inside sends the alarm!  Cancer Treatment!  Radium-223 can be placed directly in the middle of a tumor to kill the cancer cells. Because of the low- penetrating power, alpha particles can’t reach to the healthy cells!  SpaceCraft Heat and Electricity!  Plutonium-238 emits alpha particles and a bunch of heat, which keeps the spacecraft warm, and excess heat is turned into electricity to run the craft!

8. 2. BETA PARTICLES 0 -1 β = 0 -1 e - identical to electron, but still comes from the nucleus - can be stopped by aluminum - very high speed (9/10 the speed of light) - formed when a neutron becomes a proton (advanced particle physics stuff…)

9. USES OF BETA RADIATION  PET Scans and other Tracers!  Short-lived radioactive elements are injected into your vein and allowed to travel through the body during PET Scans. A machine is then used to see where these atoms moved about through your body by detecting the beta particles! Can also be used in machinery or pipe systems to look for leaks or cracks!  Cancer Treatment!  Strontium-90 is often used to produce a consistent amount of beta particles, which can be directed at a tumor to kill off specific cells! Healthy cells may be damaged as well, but they are better at repairing themselves than cancer cells.

10. 3. GAMMA RAYS 0 0 γ or γ - not a particle at all so has no element symbol - never emitted on its own, always with alpha or beta - high frequency electromagnetic waves - have no mass but possess energy - most penetrating – stopped only by thick Pb or concrete - move at the speed of light

11. USES OF GAMMA RADIATION  Also Tracers!  Used the same way as Beta radiation tracers  Cancer Treatment!  Radium and Cobalt are often used to produce a consistent amount of high energy gamma rays. They can either be directed like a knife right at the tumor, or injected into the body where it targets cells that rapidly multiply!

12. What makes up an atom? Radioactivity Gives Clues Experiment by Henri Becquerel and Marie Curie(1896): Radioactivity—the spontaneous emission of radiation. The radiation is passed between two electrically charged plates and detected by a photographic plate. The particles’ charges as well as their masses affect where they hit the plate.

13. RESEARCH BREAK CITE YOUR SOURCES!!!!! 1.Find a scientists that have lead to the advancement of nuclear chemistry (discovering particles, uses, safety, etc) and explain what they did in a paragraph. 2.Make a chart to compare alpha, beta, and gamma radiation. Include the symbols, penetrating ability, and find the dangers and affects of exposure. 3.Find some websites that are for nuclear power plants and nuclear energy and some that are against it. Compare what you find and make a decision about how you feel about it.

14. OTHER AREAS OF NUCLEAR CHEMISTRY -Nuclear Fission: -large atoms break apart into smaller ones -Nuclear Fusion: -small atoms combine to make larger ones -Both processes release massive amounts of energy!

15. FISSION -Begins at ordinary temps, but needs high-speed neutrons to hit a large nucleus -Releases 2 lighter nuclei, a couple high-speed neutrons, and LOTS of energy! -These new neutrons can then hit more large nuclei and keep the process going = CHAIN REACTION! -The atomic bomb is a fission bomb, where we want the chain reaction -This is the process which occurs in a nuclear power plant, but we avoid the chain reaction part FISSION OF U-235

16. FISSION

17. CHAIN REACTION We can block a chain reaction by putting small and stable atoms around the uranium, so that the neutrons are blocked

18. FUSION - process in which light elements combine to form heavier elements ie: 4 H +  4 2 He + 2 0 1 e + energy 3 H + 2 H  4 2 He + 1 0 n + energy - - Needs extremely high temps to occur, in the millions of degrees Celcius! - - This is what is happening in stars then! - The hydrogen bomb is a fusion bomb, which gets the temps required by using a fission bomb - Have not been able to beneficially do this on Earth yet. Either it’s destructive, or takes as much energy to start it as we get out of it.

19. FUSION

20. EINSTEIN’S EQUATION -Two scientists (Hahn and Strassman) found that the overall mass decreases after a fission reaction occurs. -This is due to what is called the Strong Force or Strong Nuclear Force, which is what helps to hold the nucleus together. By breaking apart the nucleus, some of the this force is no longer needed and goes away.

21. THE TRUTH ABOUT SCIENCE

22. EINSTEIN’S EQUATION -Einstein researched this further and came up with his famous E=mc 2 which applied to nuclear fission, fusion and radioactive decay (all that alpha, beta, and gamma stuff we just learned!) True for fusion because 2 nuclei each have their own Strong Force, and not all of it is needed when they become 1 nucleus. E=mc 2 shows the relationship between mass and energy. C is the speed of light, or 300,000,000 m/s. By squaring it in the equation, even the smallest amount of mass that changes into energy produces HUUUUUGE amounts of energy. FARRR more energy available than ANY regular chemical reaction.

23. EINSTEIN’S EQUATION Converting 1 kg of Uranium-235 into energy. E = mc 2 E = (1kg) * (300,000,000m/s) 2 E = 90,000,000,000,000,000 Joules E = 9x10 16 joules Energy produced burning 1 kg of coal (not using E = mc 2 ) E = 31,000,000 joules E = 3.1 x 10 7 joules So: if 1kg of Uranium-235 disappeared and turned into energy will produce over 1 trillion times the energy of 1kg of coal being burned! Granted, it’s very hard to get this much Uranium to turn into energy all at once, but it can happen slowly in those power plants of ours…

24. EINSTEIN’S EQUATION You Try! E = mc 2 E is energy in joules, m is mass in kg, and c is 3.0 x 10 8 m/s 1)If 5 grams of uranium is converted into energy through fission, how much energy is produced? 2)If 1.13 x 10 13 J of energy is produced during hydrogen fusing in the sun, how much mass was lost? 3)If 3.15 x 10 7 J of energy is produced during the alpha decay of plutonium, how much mass was lost? Fun Fact: The mass in #3 is about the size of a grain of sand. This is enough energy to power an incandescent bulb for 5.2 days!

25. RULES FOR NUCLEAR REACTIONS Two parts to every reaction: Reactants Products Starting materials  Ending materials Means a reaction has happened Laws of Conservation: Certain properties are maintained throughout any reaction, nuclear or chemical - charge - mass and mass numbers - we just talked about how this isn’t exactly true, but the mass change is small enough that it won’t affect what we’re doing here

26. BALANCING NUCLEAR REACTIONS We can predict the type of radiation or the resulting atom of a nuclear reaction if we know enough information. Ex: 239 94 Pu + 4 2 He  1 0 n + _______ What kind of particle is this? What do you think this is?

27. Particles: Alpha: 4 2 He or 4 2 α Beta: 0 -1 e or 0 -1 β Proton: 1 1 p or 1 1 H Neutron: 1 0 n Gamma: 0 0 γ or γ

28. WHAT’S THE POINT OF NATURAL NUCLEAR REACTIONS? Trying to reach a STABLE nucleus! (at least to lead, Pb) This often doesn’t happen with one reaction! Let’s take a look at the process at which radium-226 goes through to become stable…

29. What 2 things are changing with each alpha decay? What 1 thing changes with each beta decay?