Polar Bonds, Dipoles and
Hybridization
DIPOLE MOMENT
HF
• Dipole moment: Vector addition of the magnetic moment of
polar bonds
• And that means…….
• In one bond (2 atom) molecule if the bond is a polar the
molecule is polar (aka has a dipole moment)
• In multi-bond atoms you need to look at the geometry.
• Look at polar bonds and there directions
• Bonds in opposite directions cancel.
• Bonds in same direction add.
ClF3
ANOTHER EXAMPLE: XEF2CL2
Two Possible Arrangements
Cl
F
Going back to our Previous Structures.
(we’ll skip some of them and I’ll alter a few for this purpose. )
O
All bonds polar
E.G:
Polar bond
C
F
M.G.
H
H
Not very Polar bonds
E.G:
N
O
All bonds polar
Polar?
O
M.G.
Polar?
F
Xe
F
E.G:
M.G.
F
Polar?
Going back to our Previous Structures.
(we’ll skip some of them and I’ll alter a few for this purpose. )
+0
O
S
-1
O
E.G:
+0
O
+0
O
-1
All bonds polar
M.G.
Polar?
MICROWAVES: QUANTUM MECHANICS AT WORK.
• http://phet.colorado.edu/en/simulation/microwaves
• Polar water molecules are excited rotationally by microwaves
• Friction heats up food
• Why can’t you put metal in a microwave?
• Lightbulb video
• https://www.youtube.com/watch?v=id9ll_RwT_U
HYBRIDIZATION IN SUMMARY
• Draw Lewis Structure
• Figure out the arrangement of electron pairs and bonds
• Determine steric number:
• number bonded atoms+electron pairs
• give you number of hybrid orbitals needed, and therefore hybridization
• If you need: then
• 6: sp3d2
(1+3+2=6)
• 5: sp3d1
(1+3+1=5)
• 4: sp3
(1+3=4)
• 3: sp2
(1+2=3)
• 2: sp
(1+1=2)
ATOMIC ORBITAL HYBRIDIZATION
p
p
p
sp
hypridization
p
p
p
E
sp
p
p
sp2
hypridization
p
E
sp2
sp
s
sp2
sp2
s
Things to notice:
Combine # of orbitals, get same # of hybrid orbitals
p
p
p
spx is the “name” of the orbital, just like s and p were
sp3
hypridization
E
sp3
s
sp3
sp3 sp3
Energy of spx orbital is between that of the s and the p
orbital
Going back to our Previous Structures.
(we’ll skip some of them and I’ll alter a few for this purpose. )
O
Polar bond
C
H
H
Not very Polar bonds
E.G:
M.G.
Polar?
Bonding orbital cartoon
(s orbital on Oxygen left out)
Going back to our Previous Structures.
(we’ll skip some of them and I’ll alter a few for this purpose. )
E.G:
N
O
All bonds polar
O
M.G.
Polar?
What is the hybridization
on carbon?
Going back to our Previous Structures.
(we’ll skip some of them and I’ll alter a few for this purpose. )
All bonds polar
F
F
Xe
F
E.G:
M.G.
F
Polar?
What is the hybridization
on carbon?
Why do we need MO theory if we have hybridization?
(plus MO diagram building practice snuck in)
• Part A) Draw the Lewis structure of
oxygen.
• Decide based on the lewis structure what
the bond order should be and using
valance bond theory whether it is
paramagnetic or diamagnetic.
2p
2p
2s
2s
Atomic
Atomic
MO DIAGRAM OF OXYGEN
Molecular
2p
• Part B) Draw the MO diagram of oxygen
• Decide based on the MO structure, what
the bond order should be and whether it is
paramagnetic or diamagnetic.
• Tip: if possible, try doing this from scratch
without looking at your notes from the
video. See what mistakes you make and
what you forget to do.
O2