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Unformatted text preview: Chem 210/ WANG / Chapter 9C
MO Theory How about Hetero-Nuclear
molecules such as: CO, NO & HF?
Ref: Figure 9.48 2px 2py CO, NO use normal
MO order of filling as
HF does not: Energy σ∗ •because 1s (H) is higher
in energy than 1s(F).
•1s(H) is closer to 2p(F)
and interacts with it
to make a σ bond.
•Other AO’s of F do not
AO of H MO of HF AO of F
1s Note: the MO energy levels in the lecture slides as
presented on Wed, Sept 30th, is obtained from
another textbook. It DOES NOT follow the same
order as that of O2. • Upon searching further on several
trustworthy web sites, I found out
this discrepancy occurs among many
• It DOES appear that the Central
Science textbook is NOT accurate.
• MO diagrams for both NO and CO do
NOT follow the same order as that of
O2. But they are closer to that of N2.
See attached references. Explanation to discrenpancy found in textbooks. The Central
version of The MO
diagram for NO σ*2s π*2p 2p π2p possible Lewis
σ2p 0 2s 2s AO of N O 2p p possible Lewis
structures π2p 0 AO of O σ*2s 2s 0 N +1 N σ O -1 σ*2s 2p 0 N Energy Energy π*2p 2p The MO diagram for
NO obtained from
similar to that of N2. σ*2s O -1 2s AO of N +1 N O AO of O σ2s σ2s MO of NO MO of NO Note these MO diagrams for NO and CO
are similar to that of N2 / not that of O2. http://www.chm.davidson.edu/vce/MolecularOrbitals/ Fall 2009 UM-SJTU JI Which order should you use?
• For hetero-nuclear diatomic
heteromolecules or ions, you do not need to
figure it out or memorize which one
is which order.
• You will just take what is given, and
answer the question accordingly.
• If a question states that the
energy level is similar to that of
O2, then use that order.
• If it says the order is the same as
N2, then use this order. 1 ...
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- Spring '09