Heteronuclear Diatomics

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Heteronuclear Diatomics
Same principles apply Number of MOs must
equal number of AOs Only valence Aos are
considered Only AOs of similar symmetry (both s
or both p) are combined We combine AOs of
similar energy New for heterodiatomics
Atomic orbitals for each atom will now have
different energies Unused AOs will retain their
shape and energy in the molecule
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Molecular Orbitals for HF

• Consider the valence atomic orbitals of hydrogen
  and fluorine
• Which AOs will combine to make MOs?
• Which AOs will not mix (and therefore still look
  like an AO)?

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HF MOs
MOs formed from mixing
Unchanged AOs
Sorting out the energies
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HF MO diagram
Molecular Orbitals that do not contribute to bond
or anti-bonding are called Orbital types are
still based on their properties. What bond order
is predicted by the Lewis structure? What bond
order is predicted by the MO diagram? What does
the MO diagram say about the lone pairs of the
Lewis structure?
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The CO MO Diagram
The AOs involved are so we would expect this
diagram resemble that of Sorting out the
energies is not a simple matter so we use Hyper
chem.
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The MOs of CO
Classify as s or p. Bonding, non-bond or
antibonding. Polarized to C or O?
What is the BO from the MO diagram? Lewis
structure?
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AlN (Aluminum Nitride)

• MO theory is also valid for free molecules of
  ionic compounds which can usually only be made
  under high vacuum conditions.
• Consider the valence atomic orbitals of aluminium
  and nitrogen
• Which AOs will combine to make MOs?

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• What do we expect the MO diagram to look like for
  AlN?
• In fact, some MOs of AlN are so close in energy
  that different computational methods disagree on
  what order to rank them.