Ch08

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Ch08

  1. 1. The Atom Chapter 8 Great Idea: All of the matter around us is made of atoms, the chemical building blocks of our world
  2. 2. Chapter Outline <ul><li>The Smallest Pieces </li></ul><ul><li>The Structure of the Atom </li></ul><ul><li>When Matter Meets Light </li></ul><ul><li>The Periodic Table of the Elements </li></ul>
  3. 3. The Smallest Pieces
  4. 4. The Smallest Pieces <ul><li>Democritus </li></ul><ul><ul><li>Cut matter to reach smallest piece </li></ul></ul><ul><ul><li>Called “the atom” or “uncuttable” </li></ul></ul><ul><ul><li>All material formed from atoms </li></ul></ul>
  5. 5. Dividing a Bar of Gold
  6. 6. Elements <ul><li>John Dalton </li></ul><ul><ul><li>Father of modern atomic theory </li></ul></ul><ul><ul><li>Cannot break down elements </li></ul></ul><ul><ul><li>Elements composed of atoms </li></ul></ul><ul><ul><ul><li>Example: Water molecule is 1 oxygen atom and 2 hydrogen atoms </li></ul></ul></ul>
  7. 7. Envisioning Atoms
  8. 8. Are Atoms Real? <ul><li>Evidence for the reality of atoms </li></ul><ul><ul><li>Behavior of a gas </li></ul></ul><ul><ul><li>Chemical combinations </li></ul></ul><ul><ul><li>Radioactivity </li></ul></ul><ul><ul><li>Brownian motion </li></ul></ul><ul><ul><li>X-ray crystallography </li></ul></ul><ul><ul><li>Atomic-scale microscopy </li></ul></ul>
  9. 9. The Behavior of a Gas <ul><li>Bernoulli </li></ul><ul><ul><li>Atoms have mass and velocity and thus kinetic energy </li></ul></ul><ul><li>Decreasing volume increases pressure </li></ul><ul><li>Increasing temperature increases pressure </li></ul>
  10. 10. The Behavior of Gases
  11. 11. Chemical Combinations <ul><li>Dalton applied law of definite proportions </li></ul><ul><ul><li>Elements combine in a specific ratio of weights </li></ul></ul><ul><ul><ul><li>Ex: Water is 8 parts oxygen to 1 part hydrogen </li></ul></ul></ul>
  12. 12. Chemical Combinations (cont.) <ul><li>Ratio of weights is a small whole number </li></ul><ul><ul><li>Ex: 12 lbs carbon can combine with either 16 lbs or 32 lbs of oxygen </li></ul></ul><ul><li>Implication: some units of elements are fundamentally indivisible </li></ul>
  13. 13. Radioactivity <ul><li>Radioactivity </li></ul><ul><ul><li>Discovered in 1896 </li></ul></ul><ul><li>Phosphors flash when hit by radiation </li></ul><ul><li>1903 demonstration of the twinkling caused by this effect </li></ul>
  14. 14. Brownian Motion <ul><li>Brownian motion: erratic, jiggling motion </li></ul><ul><ul><li>Pollen grains suspended in water </li></ul></ul><ul><li>Einstein: motion is random collisions of atoms </li></ul><ul><ul><li>Predicted particle movement </li></ul></ul><ul><li>Perrin tested and confirmed Einstein’s predictions </li></ul>
  15. 15. X-ray Crystallography <ul><li>Developed in 1912 </li></ul><ul><li>Demonstrates arrangement of atoms in crystals </li></ul>
  16. 16. Discovering Chemical Elements <ul><li>Electrolysis </li></ul><ul><li>Mendeleev </li></ul><ul><li>Current periodic table </li></ul><ul><ul><li>112 elements </li></ul></ul><ul><ul><ul><li>92 found in nature </li></ul></ul></ul>
  17. 17. <ul><ul><li>Helium, carbon, aluminum, copper, gold </li></ul></ul>Everyday Elements
  18. 18. The Structure of the Atom
  19. 19. The Structure of the Atom <ul><li>Joseph Thomson identified electron </li></ul><ul><ul><li>Negatively charged </li></ul></ul><ul><ul><li>Smaller and lighter than smallest atom </li></ul></ul><ul><li>Atoms are NOT fundamental building blocks, but are made up of smaller more fundamental particles </li></ul>
  20. 20. The Atomic Nucleus <ul><li>Ernest Rutherford determined atomic structure </li></ul><ul><li>Concluded </li></ul><ul><ul><li>Atom has nucleus at center surrounded by electrons </li></ul></ul><ul><li>Later discoveries found nucleus is composed of protons and neutrons </li></ul>
  21. 21. Rutherford’s Experiment
  22. 22. Important Terms Related to Atoms
  23. 23. Why the Rutherford Atom Couldn’t Work <ul><li>Why? </li></ul><ul><ul><li>Object in circular orbit is accelerating </li></ul></ul><ul><ul><li>Accelerated electrical charge emits electromagnetic radiation </li></ul></ul><ul><ul><li>Electrons giving off energy while orbiting </li></ul></ul><ul><ul><ul><li>Result: electrons spin toward nucleus and eventually atom ceases to exist </li></ul></ul></ul><ul><li>Rutherford atom exists <1min </li></ul>
  24. 24. The Nuclear Regulatory Commission <ul><li>Logo: highly stylized atomic model </li></ul>
  25. 25. When Matter Meets Light
  26. 26. Niels Bohr
  27. 27. The Bohr Atom <ul><li>First working model of atom </li></ul><ul><li>Energy levels for electrons </li></ul><ul><ul><li>Specific distances from nucleus </li></ul></ul><ul><ul><li>Electrons exist with no radiation </li></ul></ul><ul><ul><li>Electrons cannot exist between allowed distances (energy levels) </li></ul></ul>
  28. 28. Bohr Atom
  29. 29. Electron Energy Levels
  30. 30. Atomic Model
  31. 31. Photons: Particles of Light <ul><li>Photon absorbed </li></ul><ul><ul><li>Used to move electron to a higher energy state </li></ul></ul><ul><li>Photon emitted as electron moves to lower energy state </li></ul>
  32. 32. Photons: Particles of Light
  33. 33. Photons - cont. <ul><li>Quantum leap or jump -electron disappears from original location and reappears in final location- never at positions in between </li></ul>
  34. 34. Energy in Bohr Atom <ul><li>Energy required to leave ground state </li></ul><ul><ul><li>Absorb photon </li></ul></ul><ul><ul><li>Heat </li></ul></ul><ul><ul><ul><li>Increases collisions </li></ul></ul></ul>
  35. 35. Spectroscopy <ul><li>Atoms emit and absorb different photons </li></ul><ul><li>Depends on differences between energy levels </li></ul><ul><li>Each atom has distinct set of photons </li></ul><ul><li>Spectrum: all photons emitted by an atom </li></ul><ul><ul><li>Used for identification </li></ul></ul>
  36. 36. Na, K, and Li – Give Distinctive Colors to a Flame
  37. 37. Spectroscopy – cont. <ul><li>Glass prism </li></ul>
  38. 38. Spectroscopy – cont. <ul><li>Line spectra for H, Na, and Ne </li></ul>
  39. 39. The Periodic Table of the Elements
  40. 40. The Science of Life <ul><li>Spectra of life’s chemical reactions </li></ul><ul><ul><li>Used to determine how enzymes work </li></ul></ul><ul><ul><li>Used to identify pollutants emitted from automobile exhaust pipes </li></ul></ul>
  41. 41. Science in the Making <ul><li>Helium </li></ul><ul><ul><li>Discovery </li></ul></ul><ul><ul><li>Properties </li></ul></ul>
  42. 42. Technology <ul><li>Lasers </li></ul><ul><ul><li>Produce a beam of light </li></ul></ul>
  43. 43. Action of a Laser
  44. 44. Lasers Have Many Uses
  45. 45. Periodic Table of the Elements <ul><li>Systematizes elements </li></ul><ul><li>Columns contain similar elements </li></ul><ul><ul><li>Alkali metals: soft, silvery metals </li></ul></ul><ul><ul><li>Noble gases: colorless, odorless, and inert </li></ul></ul>
  46. 46. Periodic Table of the Elements
  47. 47. Why the Periodic Table Works: Electron Shells <ul><li>Patterns mirror arrangement of electrons in shells </li></ul><ul><li>Pauli exclusion principle </li></ul><ul><li>First shell 2 electrons, second shell 8, etc. </li></ul>
  48. 48. Electron Representation

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