2011 core ib chemistry - topic 02

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2011 core ib chemistry - topic 02

  1. 1. IB Chemistry Power Points<br />Topic 02<br />Atomic Structure<br />www.pedagogics.ca<br />Atomic Structure<br />
  2. 2. Review – Basic Atomic Structure<br />POSITIVE<br />NEUTRAL<br />CHARGE<br />CHARGE<br />ATOM<br />ATOM<br />NUCLEUS<br />ELECTRONS<br />NUCLEUS<br />ELECTRONS<br />NEUTRONS<br />PROTONS<br />PROTONS<br />NEUTRONS<br />NEGATIVECHARGE<br />POSITIVE CHARGE<br />
  3. 3. Review – Basic Atomic Model<br />
  4. 4. mass number A<br />atomic number Z<br />element symbol<br />© Addison-Wesley Publishing Company, Inc.<br />A-Z notation<br />The atomic number equals the number of protons. Each element has a unique atomic number.<br />
  5. 5. Mass Number<br />© Addison-Wesley Publishing Company, Inc.<br />mass number A = protons + neutrons<br /><ul><li>always a whole number
  6. 6. NOT the value given on the Periodic Table!</li></li></ul><li>Practice: determine the required values and write the chemical symbol in A-Z notation.<br />Chlorine-37<br />atomic #:<br />mass #:<br /># of protons:<br /># of electrons:<br /># of neutrons:<br />17<br />37<br />17<br />17<br />20<br />
  7. 7. Ions<br /><ul><li>ions are electrically charged atoms</li></ul>Neutral atom<br />gain electrons<br />lose electrons<br />positive ion<br />negative ion<br />p+ > e-<br />p+ < e-<br />cation<br />anion<br />
  8. 8. Practice: determine the required values for the negative chloride ion 37 Cl-1<br />37 Cl-1<br />atomic #:<br />mass #:<br /># of protons:<br /># of electrons:<br /># of neutrons:<br />17<br />37<br />17<br />18<br />20<br />
  9. 9. Practice: determine the required values for the positive calcium ion 40 Ca +2<br />40 Ca+2<br />atomic #:<br />mass #:<br /># of protons:<br /># of electrons:<br /># of neutrons:<br />20<br />40<br />20<br />18<br />20<br />
  10. 10. Isotopes: Atoms of the same element with different mass numbers.<br />© Addison-Wesley Publishing Company, Inc.<br />carbon-12 and carbon-14 are isotopes<br />stable<br />similar chemical properties<br />radioactive<br />
  11. 11. Radioisotopes and Their Uses<br />Radioisotopes are unstable isotopes that undergo radioactive decay. Radioisotopes have a number of uses:<br />U-235 is used as fuel in nuclear reactors<br />Co-60 is used in cancer radiation therapy<br />C-14 is used as a tracer and for archeological dating<br />Am-241 is used in smoke detectors<br />
  12. 12. Mass Spectrometer<br />A mass spectrometer is used to detect, identify and measure the abundance of different atoms, molecules or molecular fragments. <br />Mass spectrometer studies are used to determine the average atomic mass for an element. The operation of a mass spectrometer can be divided into 5 steps:<br />Vaporization<br />Ionization<br />Acceleration<br />Deflection<br />Detection<br />
  13. 13. Chapter 12<br />13<br />Vaporization: the element to be analyzed is heated and vaporized (gaseous form).<br />=><br />http://www.magnet.fsu.edu/education/tutorials/java/singlesector2/index.html<br />
  14. 14. Chapter 12<br />14<br />Ionization: the gaseous element is injected slowly into a vacuum chamber where the atoms are bombarded by electrons. This forms ions positive ions X (g) + e- X+(g) + 2 e-<br />=><br />http://www.magnet.fsu.edu/education/tutorials/java/singlesector2/index.html<br />
  15. 15. Chapter 12<br />15<br />Acceleration: the gaseous ions are accelerated through an electric field (towards a negative plate)<br />=><br />http://www.magnet.fsu.edu/education/tutorials/java/singlesector2/index.html<br />
  16. 16. Chapter 12<br />16<br />Deflection: Ions are deflected in an adjustable magnetic field oriented at right angles to the path. Heavier ions are deflected less.<br />=><br />http://www.magnet.fsu.edu/education/tutorials/java/singlesector2/index.html<br />
  17. 17. Chapter 12<br />17<br />Detection: ions of a specific mass are counted<br />=><br />http://www.magnet.fsu.edu/education/tutorials/java/singlesector2/index.html<br />
  18. 18. A sample mass spectrograph <br />Output provides the abundances of the elemental isotopes of different relative mass<br />
  19. 19. Atomic Mass is Relative<br />© Addison-Wesley Publishing Company, Inc.<br />12C atom = 1.992 × 10-23 g<br /><ul><li>atomic mass unit (amu)
  20. 20. 1 amu = 1/12 the mass of a 12C atom
  21. 21. 1 p = 1.007276 amu1 n = 1.008665 amu1 e- = 0.0005486 amu</li></li></ul><li>Average Atomic Mass<br />Avg.<br />Atomic<br />Mass<br />a weighted average of all isotopes of an element<br /><ul><li>based on the % abundance data from mass spectrometer
  22. 22. this value is found on the Periodic Table</li></li></ul><li>Avg.<br />Atomic<br />Mass<br />Average Atomic Mass<br />EXAMPLE: Calculate the average atomic mass of chlorine if its abundance in nature is 75.77% 35Cl, and 24.23% 37Cl.<br />35.48<br />amu<br />
  23. 23. Average Atomic Mass<br />Gallium has two naturally occurring isotopes, Ga-69 and Ga-71, with masses of 68.9257 amu and 70.9249 amu, respectively. Calculate the percent abundances of these isotopes<br />Average relative mass of Ga 69.7231 amu<br />Solve to get 60.1% Ga-69 and 39.9% Ga-71<br />
  24. 24.
  25. 25. All EM radiation is fundamentally the same. The only difference between a gamma ray and a radio wave is the frequency/wavelength/energy.<br />
  26. 26. White Light<br />Prism<br />Visible light is one category of EM radiation. The visible light spectrum is subdivided into six “colors”.<br />RED<br />ORANGE<br />YELLOW<br />GREEN<br />BLUE<br />VIOLET<br />
  27. 27. A continuous spectrum includes all wavelengths of radiation in a given range. <br />When white light is passed through a prism a continuous spectrum is produced.<br />
  28. 28. Colored lights do not emit all the wavelengths of the visible light spectrum. For example, a red light emits mostly wavelengths from the red end of the spectrum. <br />An energized gas sample will emit light of specific wavelengths characteristic of the gas. This is called a line spectrum<br />
  29. 29. Emission spectra are unique for each element<br />
  30. 30.
  31. 31. The Bohr model of the atom was developed using information from hydrogen emission spectrum studies. Bohr envisioned an atomic model with: <br /><ul><li>a central dense positive nucleus composed of protons and neutrons.
  32. 32. negative electrons at specific energies orbit the nucleus
  33. 33. mostly empty space. Nucleus is 10-5 times smaller than atom. </li></li></ul><li>Bohr further stated that the orbiting electrons occupy discrete energy levels. Electrons can only “jump” between energy levels if they absorb or emit a specific amount of energy. <br />
  34. 34. Bohr saw the line spectrum of hydrogen as a direct result of energized electrons releasing a specific amount of energy by emitting a photon of light at a certain wavelength. The different lines in the hydrogen spectrum were evidence for a number of different energy levels.<br />
  35. 35. higher energy<br />shorter wavelength<br />lower energy<br />longer wavelength<br />Visible spectrum for hydrogen atom<br />convergence<br />
  36. 36. Lower energy = more stable electron orbit<br />Electrons fill the lowest energy orbitals first.<br />Each orbital has a maximum possible number of electrons.As you should recall:<br />1st energy level (ground state) = 2 electrons<br />2ndenergy level = 8 electrons<br />3rd energy level = 8 electrons<br />
  37. 37. The electronic structure of an atom<br />A carbon atom has six electrons<br />1st energy level holds 2<br />2nd energy level takes the remaining 4<br />The electron structure for carbon would be written as 2,4<br />The electrons in the outermost energy level are called valence electrons. Carbon has 4 valence electrons.<br />
  38. 38. Try writing the electron structure for calcium<br />A calcium atom has 20 electrons<br />1st energy level holds 2<br />2nd energy level holds 8<br />3rd energy level holds 8<br />4th energy level holds last 2<br />The electron structure for calcium would be written as 2,8,8,2<br />
  39. 39. Connect to Periodic Table<br />EnergyLevel<br />1<br />2<br />3<br />4<br />

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