Discussion #1 Chapter 10 CH102 2017 MOs
TF’s name:___________ Your name: ____________________ Discussion Section: ___________
1. Below on the left is an empty molecular orbital diagram of F2. Below on the right are various molecular orbitals, with
the internuclear axes shown with a dotted line. You will fill in the boxes next to the molecular orbitals in part (a).
You will fill in the circles on the molecular orbital diagram in part (b). Carefully follow the instructions below.
A
B
2p
2p
D
B
2s
2s
F2
Fluorine
E
F
a. In the box to the right of the molecular orbitals formed in F2 above, provide the proper name of each molecular
orbital (e.g. σ2s, π*, etc).
b. Match each molecular orbital on the right to the molecular orbital diagram on the left. Show your answer by
placing the letter in the circle beside the molecular orbital. Letter “B” is filled in for you.
c. In the molecular orbital diagram above, populate both the atomic and molecular orbitals with electrons by putting
arrows on the horizontal lines for F2 and the fluorine atoms. All three systems are in the ground state.
d. Using the diagram above to guide you, calculate the bond orders for the following species.
F2+ : _____________
F22- : _____________
e. Naturally Fluorine is a diamagnetic molecule. Let say in the planet far, far away we found a fluorine that is
paramagnetic: proposed and draw the molecular orbitals that Fluorine must have to be paramagnetic.
2. (At Home) C2 is naturally is diamagnetic and O2 is paramagnetic. Proposed and draw the molecular orbitals that will
make C2 paramagnetic. And Proposed and draw the molecular orbitals that will make O2 diamagnetic.
3. Atom A has a single valence electron. The ionization energy of A is 10 eV the energy of the AA bonding MO is σAA =
−13eV and of the AA antibonding MO is σ*AA = −5 Ev.
-5 eV
σ*1s
-10 eV
-13 eV
1s
1s
σ1s
a. Calculate the energy change, in eV, for the ion combination process A (g) + A(g) → AA(g).
Enthalpy of reaction = Ef – Ei
b. Calculate the energy change, in eV, for the ion combination process A- (g) + A(g) → AA-(g).
Enthalpy of reaction = Ef – Ei
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4. Atoms X and Y each have a single valence electron. The ionization energy of X is 5 eV and that of Y is 6 eV. The
bond energy of XY is 5 eV. Calculate the energy of the XY bonding MO.(Answer:-8eV)
5. Below is a molecular orbital diagram for the hypothetical molecule XY.
a) What is the first ionization energy of atom Y?
IEY =
eV
b) What is the first ionization energy of XY?
IEXY =
c) What is the bond energy of the reaction: XY+  X+ + Y
(Answer: 4eV)
d) What is the bond order of XY, XY+, XY2+, XY− ?
e) Arrange the following in order of decreasing of the bond dissociation energy XY, XY+, XY2+, XY− .
3
eV
6. For a single-electron atom X, Eσ1s = –12 eV, Eσ1s* = –7 eV, and E1s = –10 eV. What is ΔE for the reaction: X2–  X– +
X ? (Answer: 1eV)
7. Atoms A and B each have a single valence electron. The ionization energy of A is 4 eV and that of B is 6 eV. The
energy of the AB bonding MO is σAB = −9 eV and of the AB antibonding MO is σ*AB = −2 eV Calculate the energy
change, in eV, for the ion combination process A(g) + B–(g) → AB-(g).(Answer:-4eV)
!!! In Preparation for next week:
1. Review Lewis Structures.
2. Hybridized atomic orbital (sp3, sp2, sp)
Example 1: CH4 –hybridized atomic orbitals.
1s + 3p = Four of sp3 hybridized AOs
(SN=4, with 109.5° angle)
Example 2: Using hybridized atomic orbitals above, sketch the σ frame for the MO structure for C2H6
(Hint :first draw a Lewis structure, and determine steric number (SN) of the center atoms)
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Example 3: sp2 hybridized AOs
1s + 2p = Three sp2 hybridized AOs and one free p AO
perpendicular to the plane of the molecule. (SN=3, with 120°
angle)
Using the sp2 hybrid orbitals shown Sketch σ frame structure for
H2CCH2
π frame correlation diagram will look like that:
Example 4: sp hybridized AOs
1s + 1p = Two hybridized AOs and two free p AO perpendicular to the
plane of the molecule and perpendicular to each other. (SN=2, with
180° angle)
Using the sp hybrid orbitals shown, try to sketch MO structure for HCCH.
(sketch σ frame and π frame , draw π correlation diagram)
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Example 5. Draw correlation diagram for H2O using hybridized AOs .
(For help look at the example of CH4 shown below.)
Molecular Orbital Instructions:
1. Making correlation diagrams for π framework of polyatomic molecules
a. Draw Lewis Structure and any resonance structures.
i. Count the number of valence electrons
ii. Assign hybridization of all the atoms
A. Determine hybridization of the center atom(s)
B. Terminal atoms will have the same hybridization of the center atom.
b. Identify  framework
i.
Identify number of  bonds in the molecule and the number of e- involved
ii.
Identify number of lone pairs and the number of e- involved
ii.
c. Identify π framework
Determine the number of electrons involved in the π bonds
A. # π(electrons)=#Valence e- - (electrons)- lone pair(electrons)
Count the p AO’s not involved in hybridization.
iii.
Sketch the corresponding π MO.
iv.
v.
vi.
Rank them in terms of increasing energy (depending on number of loops)
Fill the π MO’s with the electrons involving in π bonds
Label the π MO’s as bonding, antibonding and /or nonbonding
i.
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