Irvington High School  AP Chemistry
Mr. Markic
Name _______________________________
Number ___ Date ___/___/___
10  Molecular Geometry & Bonding Theories
Delocalized
Molecular Orbitals
1. Both ethylene (C2H4) and benzene (C6H6) contain the C=C bond. The reactivity of ethylene is
greater than that of benzene. For example, ethylene readily reacts with molecular bromine,
whereas benzene is normally quite inert toward molecular bromine and many other compounds.
Explain this difference in reactivity.
Benzene is stabilized by delocalized molecular orbitals. The CC bonds are equivalent, rather
than alternating single and double bonds. The additional stabilization makes the bonds in benzene
much less reactive chemically than isolated double bonds such as those in ethylene.
2. Nitryl fluoride (FNO2) is very reactive chemically. The fluorine and oxygen atoms are bonded to
the nitrogen atom.
a. Write a Lewis structure for FNO2
(a) Two Lewis resonance forms are shown below. Formal charges different than zero are
indicated.
F
O
N

F
O


O
N

O
b. Indicate the hybridization of the nitrogen atom
(b) There are no lone pairs on the nitrogen atom; it should have a trigonal planar electron pair
arrangement and therefore use sp2 hybrid orbitals.
c. Describe the bonding in terms of molecular orbital theory. Where would you expect
delocalized molecular orbitals to form?
(c) The bonding consists of sigma bonds joining the nitrogen atom to the fluorine and oxygen
atoms. In addition there is a pi molecular orbital delocalized over the N and O atoms. Is nitryl
fluoride isoelectronic with the carbonate ion?
3. Describe the bonding in the nitrate ion NO3- in terms of delocalized molecular orbitals.
The ion contains 24 valence electrons. Of these, six are involved in three sigma bonds between
the nitrogen and oxygen atoms. The hybridization of the nitrogen atom is sp2. There are 16 nonbonding electrons on the oxygen atoms. The remaining two electrons are in a delocalized pi
molecular orbital which results from the overlap of the pz orbital of nitrogen and the pz orbitals of
the three oxygen atoms. The molecular orbitals are similar to those of the carbonate ion (See
Section 10.8 of the text).
4. What is the state of hybridization of the central O atom in O3? Describe the bonding in O3 in
terms of delocalized molecular orbitals.
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The Lewis structures of ozone are:
O
O
O
O
O
O
The central oxygen atom is sp2 hybridized (AB2E). The unhybridized 2pz orbital on the central
oxygen overlaps with the 2pz orbitals on the two end atoms.
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