Problem 1
After reading the theory part draw the MO diagrams for the
following diatomic omonuclear molecules:
H2, B2, C2, N2, O2, Ne2, F2
choosing the correct representation
**diagram2 ) clearly indicating:
diagram 1
(*diagram1
or
diagram 2
(1) if there is sp mixing;
(2) AO (2s, 2p etc.) and MO (σ, π, σ*,π*) energy levels with
the appropriate labels;
(3) the occupation of each AO, MO with arrows;
(4) the shape and phases of the combining AOs (see fig.
below)
H2 MO Diagram
B2 MO Diagram
C2 MO Diagram
N2 MO Diagram
O2 MO Diagram
Ne2 MO Diagram
MO Diagram F2
(5) Complete the following table (calculate all the quantities by
considering by neglecting the 1s shell).
B2
C2
N2
O2
Ne2
F2
electron
configuration
N. OF
OCCUPIED
MO
N. of
bonding
electrons1
N. of
antibonding
electrons2
spin
multiplicity3
Bond Order4
1. Number of electrons in bonding orbitals.
2. Number of electrons in antibonding orbitals.
3. spin multiplicity = (2S+1) where S represents the spin quantum
number.
4. [(number of electrons in bonding levels) - (number of electrons in
antibonding levels)] / 2
Problem 2
Below is an MO diagram of a π bond using two p orbitals. A nodal
plane is a plane of zero electron density formed when orbitals of
opposite phases overlap. It is indicated on the diagram below by a
dashed line.
1. How many individual AOs are shown in this diagram?
2. How many electrons are present in each atomic orbital?
3. How do the energies of the bonding and antibonding MOs
compare?
4. Another difference between the bonding MO and the
antibonding MO is the presence of a nodal plane.
Which MO contains this node?
5. For this π bond, put the electrons in the appropriate molecular
orbital(s). Explain why you chose this configuration.
6. From this diagram, does in-phase overlap (both the same color)
or out-of-phase overlap (one of each color) have to be present for
a bonding interaction?
Problem 3
Download the file C2H4.out under lecture material. This file is
containing all the informations needed to visualize the MOs of the
molecule C2H4. In oder to do that, open this file with the program
wxMacMolPlt under application:
go to Subwindow >> Surfaces >> 3D Orbital
set initially the Contour Value to 0.004 (you can modify this any
moment)
then select Orb. and press Update in the end.
Visualize all occupied molecular orbitals of C2H4 plus the 1st
unoccupied orbital (LUMO).
How many occupied orbitals you have?
Fill in the following table numbering the orbital in ascending order.
# Orbital
1
2
3
4
5
6
7
8
9
Energy
Bonding
Antibonding Orbital Type
(σ/π/σ∗/π∗)
Problem 4
Download the file C2H2.out under lecture material. This file is
containing all the informations needed to visualize the MOs of the
molecule C2H2. In oder to do that, open this file with the program
wxMacMolPlt under application:
go to Subwindow >> Surfaces >> 3D Orbital
set in initially the Contour Value to 0.004 (you can modify this any
moment)
then select Orb. and press Update in the end.
Visualize all occupied molecular orbitals of C2H2 plus the 1st
unoccupied orbital (LUMO).
How many occupied orbitals you have?
Fill in the following table numbering the orbital in ascending order.
# Orbital
1
2
3
4
5
6
7
8
Energy
Bonding
Antibonding Orbital
Type (σ/π)
Problem 5
Download the file C2H6.out under lecture material. This file is
containing all the informations needed to visualize the MOs of the
molecule C2H6. In oder to do that, open this file with the program
wxMacMolPlt under application:
go to Subwindow >> Surfaces >> 3D Orbital
set in initially the Contour Value to 0.004 (you can modify this any
moment)
then select Orb. and press Update in the end.
Visualize all occupied molecular orbitals of C6H6 plus the 1st
unoccupied orbital (LUMO).
How many occupied orbitals you have?
Fill in the following table numbering the orbital in ascending order.
# Orbital
Energy
Bonding
Antibonding Orbital
Type (σ/π)