1 / 59

Nuclear Chemistry

Nuclear Chemistry. Nuclear Power Plant in Richland, WA. 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 12 protons, U has 146 neutrons for 92 protons .

brone
Download Presentation

Nuclear Chemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Nuclear Chemistry Nuclear Power Plant in Richland, WA

  2. 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

  3. Review From Tuesday’s Lesson

  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 nucleusof 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 protonsand neutrons. • **Sometimes the rearrangements lead to unstable or radioactiveelements.

  12. Radioactive Decay—Spontaneous breakdown of an atom which results in the emission of particles, energyor 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-lives Half-life: length of time it takes for halfof 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

  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 (SO 6 ATOMS because you can’t have 0.25 of an atom!)

  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 positivecharge 2 Same as a Heliumnucleus 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 cancer and 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 years 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 negativecharge -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 electronsfrom 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) **The products are radioactive.

  35. Fission • Splitting one nucleus into smaller fragments • Nuclear power plants and most nuclear weapons rely on nuclear fission

  36. Nuclear Power • Fusion—Combining of 2 or more lightnuclei (H + H  He) **Non-radioactive products. **Requires extremely high temperatures (sun/stars) Both release LARGE amounts of ENERGY!

  37. 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

  38. 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

  39. How does a Nuclear Power Plant Work?

  40. Heat Neutrons Review: Splitting Atoms Releases Neutrons, Making Heat

  41. Steam Generator Steam produced Turbine Electricity Heat Heat Produces Steam, Generating Electricity

  42. ATOMIC WEAPONS

More Related