Breakdown, Discussion & Help With Sample Problems: What You Should Know

10.1 Valence-Shell Electron-Pair Repulsion (VSEPR) Theory and Molecular Shape

Lewis structures are flat drawings that indicate the sequence of atoms within a given molecule, the bonds that connect them, and the unshared valence electrons possessed by the atoms.

But Lewis structures are two dimensional...and our universe is three dimensional--as are most molecules. The VSEPR theory, which is outlined in Section 10.1, enables CHEM 200 students to accurately predict the shapes of molecules...and the angles of the bonds within those molecules.

CHEM 200 students should pay careful attention to Figs 10.2, 10.3, 10.4, 10.5, 10.8, and 10.10, as they provide much of the relevant information regarding the shapes of molecules.

click here for a few words about SAMPLE PROBLEM 10.1 (page 376)

click here for a few words about SAMPLE PROBLEM 10.2 (page 379)

10.2 Molecular Shape and Molecular Polarity

The important concepts bond polarity, bond angle and dipole moment, in the context of molecular shape, are discussed in Section 10.2.

click here for a few words about SAMPLE PROBLEM 10.4 (page 382)

10.3 Valence Bond (VB) Theory and Orbital Hybridization

Recall that Chapter 8 contains details of the concept of electronic configuration. In essence, electronic configuration is a kind of electron bookkeeping.

But the protocols of s, p, and d (as well as f) orbitals fails when applied to real-world molecules.

Hence, the concept of orbital hybridization was developed. Orbital hybridization is discussed in 10.3...and fleshed out in Figs 10.14 - 10.23.

Of particular importance are the drawings of ethane, ethylene, and ethyne on p 392, molecules which have sp, sp2, and sp3 hybridized carbon atoms, respectively.

click here for a few words about SAMPLE PROBLEM 10.6 (page 394)

10.4 Molecular Orbital (MO) Theory and Electron Delocalization

Molecular orbital theory complements valence bond theory in that the MO theory treats molecules as a collection of nuclei with the electron orbitals delocalized over the entire molecule.

Molecular orbitals are formed by linear combinations of atomic orbitals...and the central themes of molecular orbital theory are discussed on pages 395-397.

CHEM 200 students are first exposed to molecular orbital diagrams on p 396...along with terms such as bonding MO, antibonding MO, MO bond order, sigma (s) MO, pi (p) MO, and nonbonding MO.

exercises such as numbers 10.3, 10.10, 10.18, 10.27, 10.36, 10.52 and 10.54 are all straightforward problems of the type that are often found on CHEM 200 exams