Chapters 5/6

Chemical Bonding

2 Types of bonds

A + BA:B

Shared Pair

Covalent

A+ :B- Ionic

. .

Bonding Types

Ionic Polar Covalent NonpolarCovalent

Difference in Electronegativity

Percent Ionic

3.3 2.1 0.5 0.0

100% 50% 5% 0%

Types of Bonds

Cs - F 4.0 – 0.7 = 3.3 Ionic Bond

H - Cl 3.0 – 2.1 = 0.9 Polar Covalent

H - H 2.1 – 2.1 = 0.0 Nonpolar Covalent

Polar Covalent

H Cl

Shared electron cloud

d+ d-

(Slightly positive) (Slightly negative)

Polar Covalent – unequal sharing

Nonpolar Covalent

H H

Nonpolar Covalent – equal sharing

Properties of ionic compounds

Ionic compounds form crystals

Composed of positive and negative ions

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