Chapter Seven

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Chapter Seven
2012-11-22 14:23:53

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  1. What is the driving force behind covalent bonds?
    satisfying the octet rule by sharing electrons
  2. Covalent bonds are formed by __.
    sharing at least one pair of electrons
  3. Every covalent bond has a characteristic __ that leads to __. This is the __.
    • length
    • maximum stability
    • bond length
  4. Bond Dissociation energy
    energy required to break a covalent bond in an isolated gaseous molecule is called this
  5. What happens with energy in terms of breaking a bond?
    always add energy
  6. True or False
    Each group of atoms will have their own separate bond length.
  7. What kind of bond? 
    Metal and nonmetal
  8. What kind of bond?
    Two non-metals
  9. With ionic bonds, why is melting and boiling part higher (harder to melt)?
    the network structure makes it harder
  10. Why are covalent bonds the strongest bonds?
    when you melt them, you break the interactions, not the molecules themselves like ionic bonds
  11. What is the max amount of covalent bonds that can be formed?
  12. Ionic bonds (in terms of charge)
    full charges on elements
  13. Poalr covalent bonds
    • bonding electrons are attracted more strongly to one element than the other
    • unequal distribution
  14. What is one way to tell you have ionic substances?
    • whether it conducts electricity when dissolved in water
    • Heat it up to a liquid
  15. Diatomic atoms are always __ covalent bonds.
  16. Bond polarity is due to __ between atoms.
    electronegativity differences
  17. What is electronegativity
    the ability of an atom in a molecule to attract the shared electrons in a covalent bond
  18. What is the periodic trend in terms of electronegativity?
    • it increases from left to right
    • It decreases from top to bottom
    • Noble gases not involved
  19. % Ionic Character: __
    as a general rule for two atoms in a bond, we can calculate the electronegativity difference 
  20. What is the definition for electronegativety?
    deltaEN= EN(Y)-EN(X) for X-Y bond
  21. What are the rules for electronegativity difference?
    • If it is less than 0.5, it is nonpolar covalent
    • If greater than 0.5 but less than 2.0, it is polar covalent.
    • If greater than 2.0, it is ionic
  22. Using __, teh valence electrons in an element are represented by dots. 
    What are valence electrons?
    • electron-dot (Lewis) structures
    • those electrons with the highest principal quantum number n
  23. What does the octet rule apply to?
    • Those electrons before the 3d level
    • Atoms in the third row or lower, which are larger and can accomodate more bonded atoms
  24. What is it called when you have more than eight electrons in the valence shell?
    Where do the extra pairs go?
    • expanded octet
    • into unfileld d orbitals
  25. A molecule like O3 has a bonding characteristic that __.
    both structures are correct, but neither is correct by itself.
  26. When multiple structures can be drawn, the actual structure is an __ of all possibilities. 
    The average is called a __. What indicates this?
    • average
    • resonance hybrid
    • straight double headed arrow
  27. Tje motrate opm, NO3-, has three equivalent oxygen atoms, and its electron structure is a __ hybrid of three electron dot structures.
  28. What is formal charge?
    We determine __ and estimate the more __.
    • determines hte best resonance structure
    • formal charge
    • accurate representation
  29. How to determine formal charge?
    Formal charge= (# of valence electrons)- (# of bonding electrons/ 2)- (# of nonbonding electrons)
  30. What does VSEPR stand for?
    valence shell electron pair repulsion model
  31. VSEPR: Electrons in bonds and in lone pairs can be though t of as __ that __ one another and stay as __ as possible, thus causing molecules to assume specific shapes. 
    • charge clouds
    • repel 
    • far apart
  32. Two Charge Clouds:
    General shape
    • electron groups point in opposite directions
    • linear
  33. Three Charge Clouds?
    • electron groups lie in same plane and point to the corners of an equilateral triangle
    • angular or bent
  34. Four Charge Clouds and shapes
    • electron groups point to the corners of a regular tetrahedron
    • Four Charge Clouds with:
    • - four electrons: tetrahedron
    • - three electrons: trigonal pyramidal
    • - two: bent
  35. Five charge clouds and shapes
    • electron gorups point to the corners of a trigonal bipyramid
    • five electrons: trigonal bipyramidal
    • four electrons: seesaw
    • Three: T- shaped
    • two electrons: linear
  36. Six Charge Clouds and Shapes
    • electron groups point to the corners of a regular octahedron
    • Six electrons: octahedron
    • five electrons: square pyramidal 
    • four: square planar
  37. What is Valence Bond Theory:
    a quantum mechanical model which shows how electron pairs are shared in a covalent bond
  38. Bonds form between two __ of the same phase. A __ bond forms from head on  orbital overlap.
    • lobes
    • sigma
  39. Linus Pauling
    said wave functions from s orbitals and p orbitals could be combined to form hybrid atomic orbitals
  40. What is the hybridization of two charge clouds?
  41. What is the hybridization of three charge clouds?
  42. What is the hybridization of fourcharge clouds?
  43. The __ provides a better explanation of chemical and physical properties than the __. 
    Atomic orbital:
    molecular orbital:
    • molecular orbital (MO) model
    • valence bond (VB) model
    • probability of finding hte electron within a given region of space in an atom
    • probability of finding the electron within a given region of space in a molecule
  44. __ of orbitals is __ in energy than two isolated __ orbitals and is called a __.
    • additive combination
    • lower
    • 1s
    • bonding moleclar orbital
  45. __ of orbitals is __ in energy than two isolated __ orbitals and is called an __.
    • Subtractive combinations
    • higher
    • 1s
    • antibonding  molecular orbital
  46. Diamagnetic
    all electrons are spin-paired. It is weakly repelled by magnetic fields.
  47. Paramgnetic
    There is at least one unpaired electron. It is weakly attracted by magnetic fields.
  48. Oxygen, O2, is predicted to be __ by electron-dot structures and valence bond theory. However, it is known to be __.
    • diamagnetic
    • paramagnetic