Session Overview
| Modules | Bonding and Molecules |
| Concepts | shapes of molecules: valence shell electron pair repulsion (VSEPR), sigma and pi bonds, and octet stability |
| Keywords | bonding electron, nonbonding electron, hybridized orbital, linear combination of atomic orbitals–molecular orbitals (LCAO-MO), valence shell electron pair repulsion (VSEPR), octahedral, square pyramidal, square planar, trigonal bipyramid, polar bond, non-polar bond, planar, see-saw conformation, dipole, refractive index, electrical conductivity, covalent bond, ionic bond, expanded octet, electron domain, lone pair, molecular skeleton, Lewis structure, bonding orbital, sigma bond, pi bond, triple bond, octet rule |
| Chemical Substances | ethylene (C2H4), methane (CH4), carbon (C), acetylene (C2H2), titanium tetrachloride (TiCl4), sulfur hexafluoride (SF6), bromine pentafluoride (BrF5), iodine tetrafluoride (IF4-) |
| Applications | None |
Prerequisites
Before starting this session, you should be familiar with:
Looking Ahead
Prof. Sadoway completes the Bonding and Molecules module with a session on secondary bonding, permanent and induced dipoles, hydrogen bonding, and polarizability of molecules (Session 12).
Learning Objectives
After completing this session, you should be able to:
- Determine the shapes of molecules using hybridized orbitals, linear combination of atomic orbitals–molecular orbitals (LCAO-MO), and valence shell electron pair repulsion (VSEPR) theory.
- Write Lewis structures showing the electron distribution and molecular skeleton of compounds.
- Classify each electron as a bonding electron (B) or nonbonding electron (NB).
- Contrast the properties of covalent bonds and ionic bonds.
Reading
| Book Chapters | Topics |
|---|---|
| [Saylor] 9.1, "Predicting the Geometry of Molecules and Polyatomic Ions." | The VSEPR model; using the VSEPR model; molecular dipole moments |
Lecture Video
> Download from iTunes U (MP4 - 200MB)
> Download from Internet Archive (MP4 - 200MB)
Resources
Lecture Summary
Prof. Sadoway discusses the following:
- Hybridized bonding in molecules
- Valence shell electron pair repulsion (VSEPR)
He re-emphasizes the underlying point of this unit: equal bond energies imply equal spatial disposition, and electronic structure dictates bond disposition, which further dictates molecular architecture.
Homework
Textbook Problems
| [Saylor] Sections | Conceptual | Numerical |
|---|---|---|
| [Saylor] 9.1, "Predicting the Geometry of Molecules and Polyatomic Ions." | 1, 3, 7, 14 | none |
| [Saylor] 9.4, "Polyatomic Systems with Multiple Bonds." | 1 | none |
For Further Study
Other OCW and OER Content
| Content | Provider | Level | Notes |
|---|---|---|---|
| 5.111 Principles of Chemical Science | MIT OpenCourseWare | Undergraduate (first-year) |