1 / 34

Nuclear Chemistry: The Heart of Matter

Nuclear Chemistry: The Heart of Matter. Radioisotopes. Radioactive decay – Many isotopes are unstable Radioisotopes Nuclei that undergo radioactive decay May produce one or more types of radiation. Natural Radioactivity. Background radiation What occurs from natural sources

rosemarydavidson
Télécharger la présentation

Nuclear Chemistry: The Heart of Matter

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: The Heart of Matter

  2. Radioisotopes • Radioactive decay – Many isotopes are unstable • Radioisotopes • Nuclei that undergo radioactive decay • May produce one or more types of radiation

  3. Natural Radioactivity • Background radiation • What occurs from natural sources • >80% of radioactivity exposure

  4. Types of Radiation • Ionizing radiation – knocks electrons out of atoms or groups of atoms • Produces charged species – ions • Charged species that cause damage

  5. Nuclear Equations • Elements may change in nuclear reactions • Total mass and sum of atomic numbers must be the same • MUST specify isotope

  6. Alpha Decay • Nucleus loses  particle • Mass decreases by 4 and atomic number decreases by 2

  7. Beta Decay • Nucleus loses  particle • No change in mass but atomic number increases

  8. Positron Emission • Loses a positron • Equal mass but opposite charge of an electron • Decrease in atomic number and no change in mass • +

  9. Electron Capture • Nucleus absorbs an electron and then releases an X-ray • Mass number stays the same and atomic number decreases

  10. Gamma Radiation • Release of high-energy photon •  • Typically occurs after another radioactive decay • No change in mass number or atomic number

  11. Half-Life • Period for one-half of the original elements to undergo radioactive decay • Characteristic for each isotope • Fraction remaining = n = number of half-lives

  12. Radioisotopic Dating • Use certain isotopes to estimate the age of various items • 235U half-life = 4.5 billion years • Determine age of rock • 3H half-life = 12.3 years • Used to date aged wines

  13. Carbon-14 Dating • 99.9% 12C • Produce 14C in upper atmosphere • Half-life of 5730 years • ~50,000 y maximum age for dating

  14. Artificial Transmutation • Transmutation changes one element into another • Middle Ages: change lead to gold • In 1919 Rutherford established protons as fundamental particles • Basic building blocks of nuclei

  15. Uses of Radioisotopes • Tracers • Easy to detect • Different isotopes have similar chemical and physical properties • Physical, chemical, or biological processes • Agriculture • Induce heritable genetic alterations – mutations • Preservative • Destroys microorganisms with little change to taste or appearance of the food

  16. Nuclear Medicine • Used for two purposes • Therapeutic – treat or cure disease using radiation • Diagnostic – obtain information about patient’s health

  17. Radiation Therapy • Radiation most lethal to dividing cells • Makes some forms of cancer susceptible • Try to destroy cancer cells before too much damage to healthy cells • Direct radiation at cancer cells • Gives rise to side effects

  18. Diagnostic Uses • Many different isotopes used • Can measure specific things • Iodine-131 to locate tumors in thyroid • Selenium-75 to look at pancreas • Gadolinium-153 to determine bone mineralization

  19. Imaging • Positron emission tomography (PET) • Uses an isotope that emits a positron • Observe amount of radiation released Scans showing lung cancer (bright spot in the chest).At left - CT scan; center - PET scan; right - combined CT-PET scan.

  20. Brain tumor study and comparison of nuclear medicine and MR Upper row: fused image of nuclear medicine acquisition and MR acquisition Middle row: MR study yields excellent anatomic detail (spatial resolution) Bottom row: nuclear medicine (SPECT) images yield excellent functional information

  21. Penetrating Power of Radiation • The more mass the particle has, the less penetrating it is • The faster the particle is, the more penetrating it is

  22. Prevent Radiation Damage • To minimize damage • Stay a distance from radioactive sources • Use shielding; need more with more penetrating forms of radiation

  23. Binding Energy • Holds protons and neutrons together in the nucleus • The higher the binding energy, the more stable the element

  24. Nuclear Fission • “Splitting the atom” • Break a large nucleus into smaller nuclei

  25. Nuclear Chain Reaction • Neutrons from one fission event split further atoms • Only certain isotopes, fissile isotopes, undergo nuclear chain reactions

  26. Radioactive Fallout • Nuclear bomb detonated; radioactive materials may rain down miles away and days later • Some may be unreacted U or Pu • Radioactive isotopes produced during the explosion

  27. Nuclear Power Plants • Provide ~20% U.S. electricity • France >70% • Slow controlled release of energy • Need 2.5–3.5% 235U • Problem with disposal of radioactive waste

  28. Nuclear Fusion • Reaction takes smaller nuclei and builds larger ones • Also called thermonuclear reactions • Releases tremendous amounts of energy • 1 g of H would release same as 20 tons of coal

More Related