Chapter 5 Molecular Orbitals Figures and table removed are labeled in brackets as the chapter opener is below [Chapter opener]
5.1 Formation of Molecular Orbitals from Atomic Orbitals
Molecular Orbitals Linear Combination of Atomic Orbitals LCAO Ψ = c a ψ a + c b ψ b Ψ = molecular orbital ψ a = atomic orbital atom a c a = coefficient of atomic orbital
5.1.1 Molecular Orbitals from s Orbitals
MOs formed by s orbitals (H 2, He 2, H 2+, etc.) [Figure 5.1]
Sigma symmetry MO [Figure page 120 top]
Pi symmetry MOs [Figure page 120 bottom]
Go to Orbitron for MO movie Orbitron a gallery of orbitals
Go to Models 360 for rotatable orbitals Models 360 has molecular orbitals in a java applet
5.1.2 Molecular Orbitals from p Orbitals
[Figure 5.2]
Sigma MOs from p [Figure 5.2(a) ] Copyright 2014 Pearson Education, Inc.
Pi MOs from p [Figure 5.2(b)] Copyright 2014 Pearson Education, Inc.
Energy level diagram for p molecular orbitals [Figure 5.2 (c)] Copyright 2014 Pearson Education, Inc.
Go to Orbitron for MO movie Orbitron a gallery of orbitals
Go to Models 360 for rotatable orbitals Models 360 has molecular orbitals in a java applet
5.1.3 Molecular Orbitals from d Orbitals
Possible d MO interactions [Figure 5.3]
5.1.4 Nonbonding Orbitals and Other Factors
Energy match and MOs [Figure 5.4]
MO interaction forbidden by symmetry [Figure 5.3(b)]
5.2 Homonuclear Diatomic Orbitals 2 nd period using 2s and 2p atomis orbitals
5.2.1 Molecular Orbitals
Diatomics no s-p mixing [Figure 5.5]
5.2.2 Orbital Mixing
s and p mixing [Figure 5.6]
Illustration of s-p mixing
5.2.3 Diatomic Orbitals of the First and Second Period
No mixing O 2 and F 2 [Figure 5.6(a)]
s and p mixing Li 2, Be 2, B 2, C 2, [Figure 5.6(b)] and N 2
Bond order For molecular orbitals, bond order is calculated by Bond order = ½ (Bonding electrons Antibonding electrons)
Population of orbitals for second row homonuclear diatomcs [Figure 5.7]
Bond Distances in carbon and oxygen diatomics [Two tables on page 128]
[Figure 5.8] Bond distances
Covalent radii = ½ bond length [Figure 5.9]
[Table 5.1]
5.2.4 Photoelectron Spectroscopy skip
5.3 Heteronuclear Diatomic Molecules
5.3.1 Polar Bonds
[Table 5.2]
Relative orbital energies [Figure 5.12]
HF [Figure in examnple 5.3 page 137]
5.3.2 Inorganic Compounds and Molecular Orbitals
[Figure 5.14] LiF
CO [Figure 5.13]
Go to Models 360 for rotatable orbitals Models 360 has molecular orbitals in a java applet
5.4 Molecular Orbitals for Larger Molecules
5.4.1 FHF-
FHF - Introducing the group orbital approach The formation of FHF - can be thought of as separation of F 2 orbitals and insertion of H - in the center.
F2 group orbitals [Figure 5.16]
The bonding and antibonding orbitals in FHF - [Figure 5.17]
FHF- MO diagram [Figure 5.18]
5.4.2 CO 2 the Symmetry Adapted Linear Combination (SALC) approach
Steps in the symmetry adapted MO approach Assign point group to molecule. Use a lower symmetry for linear Assign a coordinate system. Highest axis = z. Construct a reducible representation of the s orbitals on the outer atoms. Carry out symmetry operations, and character = 1 if atom moves other wise zero. Repeat for p orbitals on outer atom, and character = 1 if p is same, -1 if the negative, and zero if it moves. Reduce the representation to get the symmetry of the group orbitals. (Construct the group orbitals.) Match group orbitals with orbitals on the central atom of the same symmetry. Construct MO from interaction of orbitals of the same symmetry Construct the MO energy level diagram
CO 2 Point group is D h. Infinite axis. Easier to use lower Symmetry sub group D2h. Molecular axis to right is z. x axis straight up. y axis is pointing straight out of page.
Outer s orbitals reducible rep. [Table page 144 top] Reduction [Table page 144 bottom]
Outer p orbitals reducible rep. Reduction not shown, symmetries on next page [Table page 144 middle]
[Figure 5.18] CO 2 group orbitals
[Page 145] D 2 h character table
Central atom (C) orbital symmetries [Figure 5.18] s =Ag (two group orbitals p x = B 3 u (one) p y = B 2 u (one) p z = B 1 u (two) Note B 2 g and B 3 g has no match on central atom. These MOs are non-bonding
Symmetries of the central atom orbitals [Figure 5.19]
Energy match of C and O [Figure 5.22]
[Figure 5.20] Ag and B 1 u s MOs
[Figure 5.21] A g and B 1 u p MOs
[Figure 5.23] B 2 u and B 3 g p MOs
[Figure 5.24] B 3 u and B 2 g p MOs
CO 2 MO energy levels [Figure 5.25]
5.4.3 H 2 O
[Figure 5.26] H 2 O
[Table 5.3]
H 2 O [Figure 5.27]
Drawings of water molecular orbital formation [Table 5.4]
H 2 O MO energy [Figure 5.28] levels
5.4.4 NH3
NH 3 [Figure 5.29]
[Table 5.5]
Using the projection method to generate orbitals Project one orbital through every symmetry operation [Table middle of page 153] Multiply the projection by the characters of the orbital symmetries [Table bottom of 153] Copyright 2014 Pearson Education, Inc.
The resulting group orbitals [Three figures in the margins of pages 154 and 155]
Copyright 2014 Pearson Education, Inc. [Table 5.6]
NH 3 MO energy levels [Figure 5.30]
skip 5.4.5 CO 2 revisited with projection operators
5.4.6 BF3
Note, I have two separate pdf files on BF 3 that will be on the web page
BF 3 orbital generation [Figure 5.31]
BF 3 MO energy levels [Figure 5.32]
5.4.7 Hybrid orbitals
Hybrid orbital procedure for CH 4 [Figure and table from page 162]
Hybrid orbitals [Figure 5.34]