Inorganic Chemistry

1
Lectures 1-5 and 6

• Introduction
• History of Periodic Table
• Quantum-mechanics basis of the Periodic Table
• Periodic properties of atoms
• Molecular symmetry
• Symmetry elements and operations
• Point group
• Molecular properties dipole moment (67-69),
  chirality(102-103), IR vibrations (103-110)

2
From Molecular Formula to Properties

• Molecule
• Structure
• Point Group
• Orbital Symmetry
• Bonding Description
• Properties

3
Case Study IF5(AB5E)
C41, C43, C2
5
4
3
C41
sd2
sV2
C43
sd1
1
2
3
4
sd2
5
sV1
1
2
3
4
sd1
C2
5
sv1
sv1
1
2
4
Symmetry Elements for IF5(AB5E)
C41, C43, C2
z
C41, C43, C2
5
3
4
sV2
sV2
sd1
sd1
1
x
2
sd2
sd2
y
sV1
sV1
E C41,C43 C2 sv1, sv2 sd1,
sd2
The collection of all symmetry elements of a
molecule form a Point Group.
E 2C4 C2 2sv 2sd1
C4v
5
Point Group Assignment

• Does the molecule belong to a special group?
• linear molecules D8h (CO2) or C8v (HCl, CO)
• molecules with multiple high order axes
• Oh octahedral (SF6) or Td tetrahedral (CH4)
• Molecule doesnt have proper or improper rotation
  axes
• C1, no symmetry element except identity, CHClBrF
• Cs, molecule has only a symmetry plane, H2CCBrCl
• Ci, molecule has only an inversion center
• Molecule has only Sn axes, Sn
• Decision tree for C and D groups

6
Character Table of Point Groups(See Section
4-3-3 and Table 4-7 of textbook)
h, Order of group symmetry
operations 12122 8
Classes of operations
c, Dimension of irreducible representations
Irreducible representations
7
Character Table of the D?h Point Group
d orbitals
p orbitals
Note that the s, p, d names of the irreducible
representations coincide with the familiar names
of various bond types.
8
Topics for Quiz on February 6

• Identify symmetry elements and operations of a
  given molecule
• Know the meaning of symbols contained in
  Character Tables and how to calculate the group
  order