Section 8.4
MOLECULAR SHAPES
The shape of the molecule
determines many of its physical
and chemical properties.
ex: Shape determines taste!
Example of bitter tasting
molecule shapes.
Example of how the
shape of a sweet molecule
fits into a receptor on the taste
bud, setting off a reaction
that sends a nerve impulse.
We use
Valence
Shell
Electron
Pair
Repulsion
to determine
shape of
molecules
after Lewis
structure is
drawn
Hybridization:
when atomic orbitals mix and form new, identical hybrid orbitals
Hybridization determines shapes of molecules.
s + p + p + p + d = sp3d
Summary of Hybridization and Shapes
sp
linear
sp2
trigonal planar
sp3
tetrahedral
sp3d
trigonal pyramidal
sp3d2
Octahedral
Terms to understand:
Central atom
Bonding group
Shared pair
Unshared pair
Bond angle
Molecular shape (class) formula
http://intro.chem.okstate.edu/1314F97/Chapter9/VSEPR.html
78. What is the octet rule and how is it used in covalent bonding?
79. Describe the formation of a covalent bond.
81. Describe the forces, both attractive and repulsive, that occur as
two atoms move closer together.
83. Give the
number of valence electrons and number of covalent bonds needed.
N
As
Br
Se
84. Locate the sigma and pi bonds.
85. In CO, CO2 and CH2O, which C-O bond is the shortest?
Strongest?
86.
87.
RESONANCE
*when more than one valid Lewis dot structure can be drawn.
* structures differ only in position of electron pairs
*atom position NEVER changes