Title: Chemical Bonding II: Molecular Geometry and Hybridization of Atomic Orbitals
1Chemical Bonding IIMolecular Geometry and
Hybridization of Atomic Orbitals
Chapter 9
2(No Transcript)
3Valence shell electron pair repulsion (VSEPR)
model
Predict the geometry of the molecule from the
electrostatic repulsions between the electron
(bonding and nonbonding) pairs.
AB2
2
0
4(No Transcript)
5VSEPR
AB2
2
0
linear
linear
AB3
3
0
6(No Transcript)
7VSEPR
AB2
2
0
linear
linear
AB4
4
0
8(No Transcript)
9VSEPR
AB2
2
0
linear
linear
AB4
4
0
tetrahedral
tetrahedral
AB5
5
0
10(No Transcript)
11VSEPR
AB2
2
0
linear
linear
AB4
4
0
tetrahedral
tetrahedral
AB6
6
0
12(No Transcript)
13(No Transcript)
14VSEPR
trigonal planar
trigonal planar
AB3
3
0
AB2E
2
1
15VSEPR
AB4
4
0
tetrahedral
tetrahedral
AB3E
3
1
16VSEPR
AB4
4
0
tetrahedral
tetrahedral
AB2E2
2
2
17VSEPR
trigonal bipyramidal
trigonal bipyramidal
AB5
5
0
AB4E
4
1
18VSEPR
trigonal bipyramidal
trigonal bipyramidal
AB5
5
0
AB3E2
3
2
19VSEPR
trigonal bipyramidal
trigonal bipyramidal
AB5
5
0
AB2E3
2
3
20VSEPR
AB5E
5
1
21VSEPR
AB4E2
4
2
22Predicting Molecular Geometry
- Draw Lewis structure for molecule.
- Count number of lone pairs on the central atom
and number of atoms bonded to the central atom. - Use VSEPR to predict the geometry of the molecule.
AB4E
AB2E
distorted tetrahedron
bent
23Dipole Moments and Polar Molecules
electron rich region
electron poor region
m Q x r
Q is the charge
r is the distance between charges
1 D 3.36 x 10-30 C m
24(No Transcript)
25(No Transcript)
26dipole moment polar molecule
dipole moment polar molecule
no dipole moment nonpolar molecule
no dipole moment nonpolar molecule
27(No Transcript)
28Dipoles (polar molecules) and Microwaves
29Sharing of two electrons between the two atoms.
Valence bond theory bonds are formed by sharing
of e- from overlapping atomic orbitals.
30(No Transcript)
31Change in electron density as two hydrogen atoms
approach each other.
32Valence Bond Theory and NH3
N 1s22s22p3
3 H 1s1
If use the 3 2p orbitals predict 900
Actual H-N-H bond angle is 107.30
33Hybridization mixing of two or more atomic
orbitals to form a new set of hybrid orbitals.
- Mix at least 2 nonequivalent atomic orbitals
(e.g. s and p). Hybrid orbitals have very
different shape from original atomic orbitals. - Number of hybrid orbitals is equal to number of
pure atomic orbitals used in the hybridization
process. - Covalent bonds are formed by
- Overlap of hybrid orbitals with atomic orbitals
- Overlap of hybrid orbitals with other hybrid
orbitals
34(No Transcript)
35(No Transcript)
36(No Transcript)
37Formation of sp Hybrid Orbitals
38Formation of sp2 Hybrid Orbitals
39Count the number of lone pairs AND the number of
atoms bonded to the central atom
of Lone Pairs of Bonded Atoms
Hybridization
Examples
2
sp
BeCl2
3
sp2
BF3
4
sp3
CH4, NH3, H2O
5
sp3d
PCl5
6
sp3d2
SF6
40(No Transcript)
41(No Transcript)
42(No Transcript)
43(No Transcript)
44(No Transcript)
45(No Transcript)
46Sigma (s) and Pi Bonds (p)
1 sigma bond
Single bond
1 sigma bond and 1 pi bond
Double bond
Triple bond
1 sigma bond and 2 pi bonds
s bonds 6
1 7
p bonds 1
47No unpaired e-
Should be diamagnetic
Molecular orbital theory bonds are formed from
interaction of atomic orbitals to form molecular
orbitals.
48Energy levels of bonding and antibonding
molecular orbitals in hydrogen (H2).
A bonding molecular orbital has lower energy and
greater stability than the atomic orbitals from
which it was formed.
An antibonding molecular orbital has higher
energy and lower stability than the atomic
orbitals from which it was formed.
49(No Transcript)
50(No Transcript)
51(No Transcript)
52- Molecular Orbital (MO) Configurations
- The number of molecular orbitals (MOs) formed is
always equal to the number of atomic orbitals
combined. - The more stable the bonding MO, the less stable
the corresponding antibonding MO. - The filling of MOs proceeds from low to high
energies. - Each MO can accommodate up to two electrons.
- Use Hunds rule when adding electrons to MOs of
the same energy. - The number of electrons in the MOs is equal to
the sum of all the electrons on the bonding atoms.
53bond order
½
1
0
½
54(No Transcript)
55Delocalized molecular orbitals are not confined
between two adjacent bonding atoms, but actually
extend over three or more atoms.
56Electron density above and below the plane of the
benzene molecule.