MHS AP Chemistry
Syllabus 9

Read Chapter 9
Study Section 9.1 & 9.2 - Molecular Shapes & VSEPR
  Tables 9.1, 9.2, and 9.3 - shapes
  Molecules without central atoms
Problems 9.2b, 9.4ac, 9.6b, 9.8, 9.10, 9.12, 9.14, 9.18, 9.20
Read Section 9.3 - Dipole moments (can you tie it in with electronegativity?)
Study  Section 9.4 & 9.5 - Covalent Bonding & Hybridization
Problems 9.28, 9.30, 9.34
Read Section 9.6 - Multiple bonds, s & p bonds, delocalized electrons and benzene
Enjoy Chemistry and Life, page 328.
Problems 9.36, 9.40, 9.42
Study Section 9.7 - Molecular Orbitals, bond order
Do 9.77 in class
Practice MO diagrams (in class) - H2, F2, O2, N2, He2, He2+, He22+, OF+ (...diatomics)
Realize THIS stuff is kind of cool!
Problems 9.48, 9.50a, 9.52, 9.54, 9.56b, 9.58
Study Section 9.8 - Diatomic molecules, paramagnetic properties, clues
Study figures 9.35 and 9.36
Problems 9.61, 9.67, 9.73abde, [9.74], 9.81, 9.88
Try Other interesting MO diagrams: CO2, NO3, CO22
   
[MHS AP Chem page]

 



Valence Shell Electron Pair Repulsion Theory (VSEPR)
  1. Draw the best Lewis dot structure.
  2. Count the number of directions that electrons leave the "center of geometry" (these are the "electron domains").  Lone pairs, any bonds, and unpaired electrons (rare) each count as "one."  [Examples:  CH4, NH3, and H2O have counts of 4, BF3, HNO, & H2CO have counts of 3; CO2 has a count of 2; IF7 has a count of 7; etc...]
  3. Distribute the things you counted so that there is maximum distance and minimum repulsion between them.  The table below gives you the shape.
    count "parent" shape
    ("electron domain geometry")
    angles hybrid
    1 -- -- --
    2 linear 180° sp
    3 trigonal planar 120° sp2
    4 tetrahedral 109° sp3
    5 trigonal bipyramid 90 & 120° dsp3
    6 octahedron (cube faces) 90° d2sp3
    7 pentagonal bipyramid 90 &  72° d3sp3
    8 cube (cube corners) (bonus!) d4sp3
  4. Figure out what goes where.  Minimize the repulsions:

  5. - electron pairs:  LP-LP > LP-BP > BP-BP   (LP = "Lone Pair"; BP = "Bonding Pair")
    - bonds:  triple > double > single
    - more electronegative is more repulsive
  6. This gives you the "parent" or "electron domain" shape.  The "daughter" or "molecular" shape is derived from this by considering only atoms connected together; lone pairs are not described in the molecular shape (see table 9.3).  Therefore, the parent shape of H2O is "tetrahedral" but the daughter or molecular shape is "bent".


Try determining the shape and hybridization of the central (bold) atom(s) for each of the following.
Click here to see the answers.
 
H2O CO CO2 NH3 SO2 NO2
O3 O2 H2CO BF3 CH4 LiH
HNO BeH2 SiH4 HCN NBr3 N2
HBO ClOH KSCN C2H6 C2H4 C2H2
(NH2)2CO PCl3 N2H4 H2 OF+ H2O2