Chemical Bonding

1
Chemical Bonding

• Sections 8.1-8.3

2
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

3
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

4
Chemical Bonds

• Strong attachment between two atoms/ions
• 3 Types
• Ionic 8.2
• Covalent 8.3
• Metallic Chap 23

5
Lewis Symbols

• Another name for electron-dot symbols
• Named for American chemist
• Shows only valence electrons
• REVIEW Nitrogen, Oxygen, Bromine

6
Octet Rule

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

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Ionic Bonding

• Electrons transferred from atom to atom
• Cation and anion formed
• Electrostatic forces exist between ions of
  opposite charge

8
Ex NaCl

• Na Cl ? Na Cl -

Each has an octet Na 2s22p6 Cl- 3s23p6
9
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

10
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

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Magnitude of Lattice Energy

• Charge of ions
• Ionic size
• Arrangement of solids

12
Trends

• Lattice Energy as charge of ions
• and radii

13
Transition Metals
14
Polyatomic Ions

• Do not forget about them!
• They are often anion (or cation for NH4) of
  ionic compounds

15
Covalent Bonding

• Majority of substances
• Sharing of pairs of electrons

16
Ionic vs. Covalent
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Lewis Structure

• Electron-dot diagrams for molecules
• Dots represent lone pairs of electrons
• A line represents shared electrons

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Lewis Structures
H-H H ö H
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Multiple Bonds

• Single bond- 1 pair of electrons are shared
• Double bond- 2 pairs are shared
• Triple bond- 3 pairs are shared

20
Single Bond
21
Double Bond
22
Triple Bond
23
Bond Length

• Distance between nuclei of atoms in a bond
• Decreases as number of shared pairs increases

24
Homework

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