Chemistry ch 12

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Chemistry ch 12
2011-01-30 14:37:32

chapter 12
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  1. Electronegativity
    the tendancy of an atom, which is bonded with other atoms, to attract other electrons
  2. Highest EN
    • Fluorine
    • 4.10
  3. lowest EN
    • Francium
    • 0.86
  4. what is EN related to?
    • postion on the periodic table
    • Down- EN decreases
    • Across- EN increases
  5. bond strenght
    how strong the bond is
  6. EN of active metals
  7. En of active nonmetals
  8. EN of noble goases
  9. Are atoms all covalent or all ionic?
    • No, it's the % ionic character
    • most are some of both
  10. If En is greater than...
    1.67, it's ionic
  11. Ionic En's
    above 1.67
  12. Covalent EN's
    below 1.67
  13. What if the EN is 1.67?
    it's half and half
  14. Pure covalent
  15. Polar covalent
  16. What holds the ions together in an ionic bond?
    The electrostatic forces between + and -
  17. Characteristics of ionic compounds
    • 1. High MP
    • 2. don't conduct electricity as a solid, but do in their molten state, when dissovled in water, & as a gas
    • 3. very soluable
    • 4. usually form well-defined crystals (solids)
    • 5. held together more strongly than compounds with covalent bonds
  18. Are ionic or covalent bonds stronger?
  19. covalent bonds form
  20. atoms of similar EN tend to
    share electrons
  21. Do covalent bnonds have electrostatic forces?
    No, they form molecules, not ions
  22. bond axis
    a line joining the nuclei of covalently-bonded atoms
  23. bond angle
    when one atom bonds with two other atoms, an angle is formed between two nuclei
  24. bond length
    the distance between two nuclei.
  25. Is bond length always the same?
    No, it varies
  26. Why does bond length vary?
    because covalent bonds stretch, bond, vibrate, and rotate.
  27. How do scientisits know about the structure of molecules?
    Infared spectroscopy
  28. Characteristics of covalent compounds
    • 1. low MP
    • 2. don't conduct electricity ever
    • 3. less soluable in water
    • 4. don't form crystals- tend to be brittle solids, liquids, or gases
  29. Metals form crystals when
    8-12 atoms of the same metal surround another metal atom
  30. why don't metals want to bond covalently?
    they want to lose 1-3 electrons
  31. why don't metals form ionic bonds?
    they all have the same attraction for their electrons
  32. metallic bonds form when
    metallic atoms crowd together and their outer energy levels overlap
  33. what cause the characteristics of metals?
    delocalized electrons
  34. characteristics of metals
    • 1. very high MP
    • 2. great conductors of electricity- the delocalized electrons carry the current
    • 3. have luster
    • 4. melleability and ductility
  35. why do metals have luster?
    the electrons jump to a higher energy level when exposed to light and then drop back, giving off light as they do
  36. what holds the atoms together in a metallic bond?
    delocalized electrons
  37. alkaili metals
    • 1 outer electron
    • the bond isn't as strong, and the metal is soft
  38. alkaline earth metals
    • 2 outer electrons
    • bonds are stronger, and the metal is harder
  39. transition metals
    • 2 outer electrons & 1 or more d electrons
    • very hard
  40. alloy
    uniformly combine 2 or more metals to form new and more usable substances
  41. alloys are not a..
    chemical change, but rather a physical blending
  42. brass
    Cu & Zn
  43. bronze
    Cu & Sn
  44. steel
    Fe & C
  45. stainless steel
    Fe, C, Cr, & Ni
  46. 14k gold
    • 42% Ag & 58% Au
    • (24k=pure Au)
  47. sterling silver
    Ag & Cu
  48. internuclear distance
    add the radii of the ions to find the distance between the nuclei
  49. why are ionic radii difficult to measure?
    their electron clouds make the distance hard to measure
  50. difference between ionic and covalent bonds
    • in covalent bonds, energy levels overlap to share one or more pairs of electrons
    • H + H = H2
  51. covalent bond lengths are almost always how long in comparison to the atomic radii?
    less than the combining radii.
  52. why do free atoms repel each other?
    • the repulsion of their respective electron clouds
    • they clouds set up a wall or shell around each atom
  53. van der Waals radius
    the distance from the nucleus to the wall or shell from the electron cloud
  54. Why do you add the van der waals radii?
    adding the van der waals radii of teo different atoms shows the minimum distance these two atoms can be to each other