Lesson Plans

Chemistry: The Central Science 9th Edition ©2003

by Brown, LeMay, and Bursten

Weeks 8–10: Chemical Bonding and Molecular Geometry

Chapter 8: Basic Concepts of Chemical Bonding
Chapter 9: Molecular Geometry and Bonding Theories

College Board Performance Objectives:

• Be able to write the Lewis symbol for any atom.
• Understand the energies involved in the formation of ionic bonds—ionization energy, electron affinity, and lattice energy.
• Predict the formula of an ionic compound between representative elements using the octet rule, and the periodic table to predict an atom's probable valence.
• Describe what happens to radius when an atom forms an ion.
• Be able to explain the variation in size of an isoelectronic series.
• Describe the nature of the covalent bond in terms of electron cloud overlap.
• Be able to show covalent bond formation using Lewis symbols.
• Be able to draw Lewis structures for bonds between atoms—single, double, and triple covalent.
• Relate bond energies to bond order.
• Explain electronegativity, how it varies on the periodic table, and its relationship to the nature of the bond between two atoms.
• Predict the polarities of bonds between any two atoms from their electonegativities or their positions on the periodic table.
• Write correct Lewis structures for any simple molecule or ion even when there is an exception to the octet rule.
• Be able to write resonance structures when no one structure is adequate.
• Relate the number of electron domains in the valence shell of an atom to the geometric arrangement of electrons around the atom.
• Understand that the relative degree of repulsion between nonbonding pairs is greater than between bonding pairs of electrons.
• Predict the molecular shape of a molecule or ion from its Lewis structure.
• Predict, from its molecular shape and the electronegativities of the atoms involved, whether a molecule is polar (has a dipole).
• Explain the types of hybridization.
• Assign the type of hybridization on the basis of the electron geometry of the valence shell of an atom.
• Describe the bonding between atoms in a molecule as or .
• Explain the concept of delocalization in bonds.
• Describe how molecular orbitals are formed from atomic orbitals.
• Explain the meaning of bonding and antibonding molecular orbitals.
• Construct the molecular-orbital energy-level diagram for a diatomic molecule or ion predicting the bond order and the number of unpaired electrons.

College Board Lab Objectives:

• Learn typical techniques used in gravimetric analysis.

Suggested Labs:

Resources:

• Instructor's Resource Manual, pp. 89–115
• Student's Guide, pp. 156–200
• Test Bank, pp. 307–382
• Instructor's Resource CD, Chapters 8–9

Pacing Guide:

• Ionic and Covalent Bonds—2 days
• Bond Polarity and Electronegativity—1 day
• Drawing Lewis Structures, Octet Rule—3 days
• Resonance and Exceptions to the Octet Rule—2 day
• Covalent Bond Strength—1 day
• VSEPR and Molecular Geometry—3 days
• Molecular Polarity—1 day
• Hybrid Orbitals—1 day
• Multiple Bonds—1 day
• Simple Molecular Orbitals—1 day
• Block Scheduling
  Ionic and Covalent Bonds, and Bond Polarity and Electronegativity should require two blocks. Drawing Lewis Structures, Octet Rule will take another two blocks. Resonance and Exceptions to the Octet Rule, and Covalent Bond Strength should fit in one block of time. VSEPR and Molecular Geometry will require two blocks of time. Molecular Polarity, Hybrid Orbitals, and Multiple Bonds will need at least one block. The extensive use of models is absolutely necessary in this chapter. Besides the text, look to the Instructor's Resource CD, the text's companion Web site, and the Internet for a source of models.

Key Words:

Suggested Exercises:
Critical thinking questions and end-of-chapter activities are included in these exercises.

• pp. 307–313, # 1, 3, 5, 7, 9, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 65, 69, 76, 79, 81, 83.
• eMedia Exercises: p. 313, # 99, 103.
• pp. 356–363, # 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 65, 67, 69, 82.
• eMedia Exercise: p. 351, # 95, 96.

Troubleshooting Tips/Error Traps:

• Ionic and covalent are extremes on a continuum of the bonding spectrum.
• Electronegativity difference alone can only establish the polarity of a bond between two atoms. To determine if a molecule is polar, we also need to also know its geometrical symmetry.
• Formal charge is not a real charge, but a way of telling how severely electrons have been moved from where they were in the Lewis symbol to where they are now in the proposed Lewis structure.
• The type of hybridization is determined from the electron domain geometry in the Lewis structure.