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Valence Bond Theory and Shape
10.4
If we only used the set of atomic orbitals to make
bonds, then the shapes of molecules would be
very limited.
For example, the porbitals only point in the x, y
and z directions. Based on the porbitals, one
would expect only octahedral shapes with 90
degree angles.
How is it possible to make a tetrahedral shape,
with its strange angles?
Valence Bond Theory and NH
3
N – 1s
2
2s
2
2p
3
3 H – 1s
1
Using the
3 2p orbitals
predict 90º
Actual HNH
bond angle is
107.3º
10.4
Example
: If the bonds form from overlap of 3 2p orbitals on
nitrogen with the 1s orbital on each hydrogen atom, what
would the molecular geometry of NH
3
be?
Orbital Hybridization and Shape
10.4
Since electrons are waves, the electrons in orbitals
can constructively and destructively interfere with
one another.
Since orbitals are the region of space that electrons
move in, that means
orbitals
constructively and
destructively interfere with one another.
Using the wave properties of electrons, we can
combine atomic orbitals to form hybrid orbitals.
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10.4
Formation of
sp
3
Hybrid Orbitals
this part
added up
this part
cancelled
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Positive 2p lobes
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 Spring '08
 ANDERSON
 Atom, Atomic Orbitals, Pi Bond, Sigma Bond, Valence, Mole, Chemical bond, sp2, hybrid orbitals

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