Presentation Transcript

1. Nuclear Chemistry Nuclear Power Plant in Richland, WA
2. Review From Tuesday’s Lesson
3. The Band of Stability Certain isotopes are more stable than others The ratio of protons to neutrons is important in determining stability Example: Mg has 12 neutrons and 12protons, U has 146 neutrons for 92 protons
4. Elements on the edge of the band or outside of the band are radioactive. Radioactive isotopes usually have more than 83 protons.
5. What holds the nucleus together? Strongnuclear force (attractive) Force pushing protons apart = repulsion due to positive charge (electrostatic force) Protons: contribute to both the attractive force (strong force) and repelling force (charge) Neutrons: contribute to the strong force (attractive) while having no charge. Act as the “glue” to bind the nucleus together
6. Binding Energy: Energy needed to hold the protons in the nucleus together (Also the energy released when an atom is split).
7. Mass and energy During nuclear reactions, there is actually a small change in mass 238.0003 g 233.9942 g + 4.0015 g = 237.9957 +
8. Mass Defect: Measured mass of an atom is LESS THAN the sum of the masses of its particles. E = mc2 Binding Energy Mass Speed of Light
9. How can we form a new element? Must have a stable nucleus and exist long enough to be detected. The neutron to proton ratio is an important factor in determining the stability of a nucleus. Some isotopes are more stable than others. Unstable isotopes undergo nuclear decay to produce atoms with lower mass.
10. Nuclear Chemistry! Nuclear chemistry: the study of the nucleus of the atom. (so, it involves neutrons and protons, not electrons!)
11. Chemical vs. Nuclear Reactions Chemical Reactions: # of atoms of each element remains unchanged Example: 2H2 + O2 2H2O Nuclear Reactions: Affect the nucleus of the atom—rearrangements of protons and neutrons. **Sometimes the rearrangements lead to unstable or radioactive elements.
12. Radioactive Decay—Spontaneous breakdown of an atom which results in the emission of particles, energy or both.
13. Stability is relative Some radioactive elements take thousands or millions of years to decay Some radioactive elements take days, minutes, or fractions of a second to decay
14. Radioactive decay is measured in Half-lifes Half-life: length of time it takes for half of a starting amount of an element to decay Ex. Radium has a half-life of 1,620 years How many years? 1620 years 100 Radium atoms 1620 years 50 Radium atoms 25 Radium atoms 1620 years 1620 years 200 Radium atoms 100 Radium atoms 50 Radium atoms 1620 years 25 Radium atoms
15. Half-life cont. A shorter half-life means an element is more radioactive because the radioactivity is released faster. Ex. Which element is more radioactive? Carbon-14 (half-life 5,720 years) or Radium-226 (half-life 1,620 years)? Radium-226
16. Your turn! You have a sample of 200 radioactive atoms and the half life is 20 years. After 100 years, how many atoms will be left? 100/20 = 5 half lives 200  100  50  25  12.5  6.25 atoms
17. Real World use of Half-Lives: Radioactive Dating Ratio of carbon 12 to carbon 14 used to determine age of once-living things! (Carbon-14 has a half-life of 5,730 years) Uranium-238 has a half-life of 4.5 billion years so is used to date rocks
18. 3 types of Radiation Alpha (a) Radiation Beta (b) Radiation Gamma (g) radiation
19. Types of Decay: The Particles 4 1. Alpha positive charge 2 Same as a Helium nucleus Alpha particle: two protons and two neutrons Alpha particles are so large they cannot penetrate very far into matter (they can be shielded with a piece of paper!!)
20. Tho-Radia Face Cream Promising instant curative and beautifying effects, Tho-Radia gained wide popularity in France during the early 1930's as a range of beauty products and perfumes. The face cream was especially popular and contained of 0.5g thorium chloride and 0.25mg radium bromide per 100g. It was even advertised as a creation of ‘Dr. Alfred Curie' although he was not a member of the Curie family and probably never existed. http://www.environmentalgraffiti.com/offbeat-news/10-radioactive-products-that-people-actually-used/1388
21. Manufactured from 1918 to 1928 by the Bailey Radium Laboratories, Radithor was a well-known patent tonic that consisted of triple distilled water containing at a least one microcurie of Radium 226 and 228 isotopes. Said to cure stomach cancerand mental illness, it was even advertised as ‘Perpetual Sunshine' until it gained notoriety when Eben Byers, an American industrialist, drank a bottle a day for four year and consequently died in excruciating pain as cancer of the jaw caused his facial bones to disintegrate. Radioactive Drinking Water Ceramic jars that added radon to drinking water were popular during the early part of the 20th century. Revigator advertised itself as ‘nature's way to health' and its ores gave off millions of tiny rays of radiation that penetrated the water, creating ‘healthful radioactive water'.
22. Radioactive Toy Set The Atomic Energy Lab first went on sale in 1951 and featured low levels of genuine radioactive material for children to experiment with. It remained on sale until the late 1970's and although the materials were labeled as ‘safe' you wouldn't find many parents today willing to let their kids play with uranium ore.
23. Radium Chocolate Radium Chocolate manufactured by Burk & Braun was sold in Germany from 1931 to 1936, advertised for its powers of rejuvenation.
24. Types of Decay: The Particles 0 2. Beta negative charge -1 An electron is emitted and a neutron is converted into a proton! beta particles = high energy electrons Beta particles also are a bit too large to penetrate you, and can be stopped with aluminum foil.
25. Types of Decay: The Particles 3. Gamma—high energy radiation High energy electromagnetic radiation No mass or charge Often emitted along with beta or alpha radiation Gamma rays penetrate, but can be stopped with lead (like x-rays!)
26. Alpha Decay Atom releases an alpha particle. Atomic # decreases becoming new element. + Notice: total starting mass equals total resulting mass: 238 = 234 + 4 total starting charge equals total resulting charge: 92 = 90 + 2 alpha particle Conclusion: in alpha decay a nucleus splits into two smaller elements, one of which is always a helium nucleus
27. Balancing Nuclear Equations Your turn! Alpha Decay 210 206 Po Pb 4 + 2 84 82
28. Beta Decay Atom releases a beta particlewith zero mass & negative charge Atomic number increases (becomes new element!) + Notice: total mass stays the same: 14 = 14 + 0 total charge stays the same: 6 = 7 - 1
29. Balancing Nuclear Equations Beta Decay 27 27 Si P 0 + -1 14 15 An electron is emitted and a neutron is converted into a proton!
30. More Practice! Francium-221 undergoes alpha decay. Write the nuclear reaction below. 217 221 Fr 4 α + At 2 85 87 Thorium-234 emits a beta particle. Write the nuclear reaction below. 234 234 Th 0 β + Pa 90 91 -1
31. The road to stability may be long! Things to notice: There are multiple steps some steps are alpha decay, some are beta decay the stable end point is an element with atomic # less than 83 (lead) there are also unstable lead isotopes which are intermediates
32. What are some uses for radioactive elements?? Atomic Weapons Nuclear Medicine Nuclear Power
33. Radiation Therapy Used to treat cancer (but yes, too much radiation can actually CAUSE cancer) Mechanism: Radiation beams knock off electrons from atoms making up DNA chains and turn them into free radicals (damaging them!) Polonium, Cobalt, Cesium & Radium are all elements used in radiation therapy.
34. Nuclear Power Fission—Splitting of a heavy nuclei (like Uranium) **Radioactive products Fusion—Combining of 2 or more light nuclei (H + H  He) **Non-radioactive products. **Requires extremely high temperatures (sun/stars) Both release LARGE amounts of ENERGY!
35. Fission Splitting one nucleus into smaller fragments Nuclear power plants and most nuclear weapons rely on nuclear fission
36. What is a Chain Reaction? Chain Reaction: A reaction in which the material that starts the reaction is also one of the products and can start another reaction. http://video.google.com/videoplay?docid=407619013941956006
37. Fusion Two nuclei combine Release large amounts of energy, but requires very high temperatures At such high temperatures, nuclei are moving so fast that collisions between them can overcome the natural repulsion of their positive charges. Examples The Sun The Hydrogen bomb
38. How does a Nuclear Power Plant Work?
39. Heat Neutrons Review: Splitting Atoms Releases Neutrons, Making Heat
40. Steam Generator Steam produced Turbine Electricity Heat Heat Produces Steam, Generating Electricity
41. ATOMIC WEAPONS
42. What are they? Nuclear weapons derive their destructive force from nuclear fusion or fission.
43. How many have there been? Two nuclear weapons have been detonated—both by the United States at the end of World War II. Where were these weapons dropped?
44. Hiroshima August 6th, 1945 Uranium 140,000 people killed (instantly, or from illness associated with radiation) Nagasaki August 9th, 1945 Plutonium 80,000 people killed (instantly, or from illness associated with radiation)
45. Manhattan Project (1941-1946) The project to develop the first nuclear weapon during WWII (U.S., Canada & the U.K.) Robert Oppenheimer: Scientific researcher (Father of the Atomic Bomb) 1945—Trinity Test (First detonation of a nuclear bomb) in New Mexico http://www.youtube.com/watch?v=RqyBzXYZPoM&feature=fvsr http://www.youtube.com/watch?v=Ru2PWmGIoB8
46. 2 Main Types of Nuclear Weapons: #1: Nuclear Fission—(Atomic Bombs)
47. 2 Main Types of Nuclear Weapons: #2: Nuclear Fusion—(Hydrogen Bombs) Use the energy of a fission bomb to heat the fusion fuel Over 1,000 times more powerful than a fission bomb! Only 6 countries have detonated one: U.S., Russia, U.K., China, France, and India
48. Nuclear Fallout—What is it? Nuclear fallout: the residual radiation hazard from a nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion. http://todayspictures.slate.com/inmotion/essay_chernobyl/
49. Hotter stars will produce larger elements “Big Bang” = H & He Cooler Stars = fuse H atoms into He Bigger/Hotter stars = slightly heavier elements made, up to Fe Supernova (explosion of star) = create heaviest elements (up to U) Video clip: minutes 55:30 to 58
50. Some light to medium-sized elements formed by simple fusion of two elements Elements heavier than iron are believed to be made by neutron capture. This is a two-step process Neutron collides and fuses with the nucleus of an atom When the nucleus is overloaded with these neutrons, it will undergo beta decay (a neutron will turn into a proton) Nucleosynthesis: forming new elements + Note: to find the product of a fusion reaction, Add up the mass #’s and atomic #’s of your starting elements Example from p92 in book Step 1: Fusion with neutrons + + Step 2: beta decay, creation of proton +