METALLIC BOND
bond found in
metals; holds metal
atoms together
very strongly
Metallic Bond
• Formed between atoms of metallic elements
• Electron cloud around atoms
• Good conductors at all states, lustrous, very
high melting points
• Examples; Na, Fe, Al, Au, Co
Ionic Bond, A Sea of Electrons
Metals Form Alloys
Metals do not combine with metals. They form
Alloys which is a solution of a metal in a metal.
Examples are steel, brass, bronze and pewter.
C. Polyatomic Ions
• NH4+
1 N × 5e- = 5e4 H × 1e- = 4e9e- 1e8e- 8e0eC. Johannesson
H
H N H
H
D. Resonance Structures
• Molecules that can’t be correctly represented
by a single Lewis diagram.
• Actual structure is an average of all the
possibilities.
• Show possible structures separated by a
double-headed arrow.
C. Johannesson
D. Resonance Structures
 SO3
O
O S O
O
O S O
O
O S O
C. Johannesson
Exceptions to the Octet Rule
• Molecules containing atoms of Group 3A
elements, particularly boron and aluminum
B
Boron trifluoride
: Cl
Al
: Cl :
:
:
:F:
: Cl :
: :
: :
:F
:
:
: F:
6 electrons in the
valence shells of boron
and aluminum
Aluminum chloride
Exceptions to the Octet Rule
• Atoms of third-period elements have 3d
orbitals and may expand their valence shells
to contain more than 8 electrons
– phosphorus may have up to 10
:
H- O-P- O-H
:
Cl :
:
Cl :
:O:
: :
O-H
:
Trimethylphosphine
: Cl
P
: : : :
CH 3
: : : :
:
CH 3 -P- CH 3
: Cl
: Cl :
Phosphorus
pentachloride
Phosphoric
acid
Exceptions to the Octet Rule
– sulfur, another third-period element, forms
compounds in which its valence shell contains 8,
10, or 12 electrons
H-O- S-O-H
:
CH 3 -S-CH 3
:
:
:
:
H-S- H
:
: O:
:
: O:
:O :
Hydrogen
sulfi de
Dimethyl
sulfoxide
Sul furi c
acid
A. VSEPR Theory
• Valence Shell Electron Pair Repulsion
Theory
• Electron pairs orient themselves in order to
minimize repulsive forces.
C. Johannesson
A. VSEPR Theory
• Types of e- Pairs
– Bonding pairs - form bonds
– Lone pairs - nonbonding e-
Lone pairs repel
more strongly than
bonding pairs!!!
C. Johannesson
A. VSEPR Theory
• Lone pairs reduce the bond angle between
atoms.
Bond Angle
C. Johannesson
B. Determining Molecular Shape
• Draw the Lewis Diagram.
• Tally up e- pairs on central atom.
– double/triple bonds = ONE pair
• Shape is determined by the # of bonding pairs
and lone pairs.
Know the 8 common shapes
& their bond angles!
C. Johannesson
C. Common Molecular Shapes
2 total
2 bond
0 lone
BeH2
LINEAR
180°
C. Johannesson
C. Common Molecular Shapes
3 total
3 bond
0 lone
BF3
TRIGONAL PLANAR
C. Johannesson
120°
C. Common Molecular Shapes
3 total
2 bond
1 lone
SO2
BENT
C. Johannesson
<120°
C. Common Molecular Shapes
4 total
4 bond
0 lone
CH4
TETRAHEDRAL
109.5°
C. Johannesson
C. Common Molecular Shapes
4 total
3 bond
1 lone
NH3
TRIGONAL PYRAMIDAL
C. Johannesson
107°
C. Common Molecular Shapes
4 total
2 bond
2 lone
H2O
BENT
104.5°
C. Johannesson
C. Common Molecular Shapes
5 total
5 bond
0 lone
PCl5
TRIGONAL
BIPYRAMIDAL
120°/90°
C. Johannesson
C. Common Molecular Shapes
6 total
6 bond
0 lone
SF6
OCTAHEDRAL
C. Johannesson
90°
D. Examples
• PF3
4 total
3 bond
1 lone
TRIGONAL
PYRAMIDAL
107°
C. Johannesson
D. Examples
• CO2
2 total
2 bond
0 lone
LINEAR
180°
C. Johannesson