Chapters 5/6
Chemical Bonding
2 Types of bonds
.
.
A +B
A:B
+
A
:B
Shared
Pair
Covalent
Ionic
Bonding Types
Percent Ionic
100%
50%
5%
0%
0.5
0.0
Difference in Electronegativity
3.3
2.1
Ionic
Polar Covalent
Nonpolar
Covalent
Types of Bonds
Cs - F
4.0 – 0.7 = 3.3
H - Cl
3.0 – 2.1 = 0.9
H-H
2.1 – 2.1 = 0.0 Nonpolar Covalent
Ionic Bond
Polar Covalent
Polar Covalent
Shared electron cloud
H
Cl
d+
d-
(Slightly positive)
(Slightly negative)
Polar Covalent – unequal sharing
Nonpolar Covalent
H
H
Nonpolar Covalent – equal sharing
Properties of ionic compounds
Composed of positive and negative ions
Ionic compounds form crystals
Ionic vs. Covalent compounds
Ionic
• Harder
• Higher melting point
• Higher boiling point
• Form crystals
• Form electrolytes
• Salt
Covalent
• Lower melting point
• Lower boiling point
• Doesn’t form electrolytes
• Sugar
Metallic bonds
Sheet of positive ions surrounded by mobile electrons
Metallic bonding
• Electrons are randomly spaced
– Free to move around
– Good conductors of heat and electricity
– Called “electron sea”
• Properties of metals
– Malleable – able to be bent or shaped
– Ductile – able to be drawn into a wire
VSEPR
• Valence shell electron pair repulsion theory
– Electrons want to be as far apart as possible
– “molecular geometry”
•
•
•
•
Linear – AB2
Bent – AB2e2
Triangular Planar – AB3
Tetrahedral – AB4