Chemical Bonding

Sections 8.1-8.3

Objectives• Identify types of chemical bonds• Revisit Lewis symbols• Analyze ionic bonding • Compare and contrast ionic and

covalent bonding• Identify single, double, and triple

bonds

Key Terms• Chemical bond• Ionic bond• Covalent bond• Metallic bond• Lewis symbol• Octet rule

• Lattice energy• Lewis structure• Single bond• Double bond• Triple bond• Bond length

Chemical Bonds

• Strong attachment between two atoms/ions

• 3 Types– Ionic: 8.2–Covalent: 8.3–Metallic: Chap 23

Lewis Symbols• Another name for electron-dot

symbols• Named for American chemist• Shows only valence electrons

• REVIEW: Nitrogen, Oxygen, Bromine

Octet Rule

• Atoms tend to gain, lose, or share electrons to get 8 valence electrons–Full s and p –Many exceptions BUT good

framework

Ionic Bonding • Electrons transferred from atom to

atom– Cation and anion formed

• Electrostatic forces exist between ions of opposite charge

Ex: NaCl

Na + Cl Na+ + [ Cl ]-

Each has an octet

Na+ : 2s22p6

Cl- : 3s23p6

Energetics of Ionic Bond Formation

• Formation is very exothermic– Lose of electron is endothermic–Gain of electron is exothermic

• Attraction of opposite charges releases energy when stabilized

Lattice Energy• Measure of stabilization• Energy required to completely

separate a mole of a solid ionic compound into its gaseous ions

• Table 8.2 page 305+ if separating- if forming

Magnitude of Lattice Energy

• Charge of ions• Ionic size• Arrangement of solids

Trends

• Lattice Energy as charge of ions

and radii

Transition Metals

Polyatomic Ions

• Do not forget about them!

• They are often anion (or cation for NH4+) of ionic compounds

Covalent Bonding

• Majority of substances• Sharing of pairs of electrons

Ionic vs. Covalent

Lewis Structure

• Electron-dot diagrams for molecules

• Dots represent lone pairs of electrons

• A line represents shared electrons

Lewis Structures

H-H

H ö:

H

Multiple Bonds• Single bond- 1 pair of electrons are

shared• Double bond- 2 pairs are shared• Triple bond- 3 pairs are shared

Single Bond

Double Bond

Triple Bond

Bond Length

• Distance between nuclei of atoms in a bond

• Decreases as number of shared pairs increases

Homework

• 8.8-8.24 and 8.30-8.34 on page 336-337–Black problems only–Due Monday 3/23