CHEM 14A Study Guide - Midterm Guide: Molecular Orbital Theory, Diatomic Molecule, Orbital Hybridisation
Document Summary
According to the vsepr model, regions of high electron concentration take up positions that maximize their separations; electron pairs in a multiple bond are treated as a single unit. The shape of the molecule is then identified from the relative locations of its atoms. Lone pairs distort the shape of a molecule so as to reduce lone pair-bonding pair repulsions. A diatomic molecule is polar if its bond is polar. A polyatomic molecule is polar if it has polar bonds arranged in space in such a way that the dipole moments associated with the bonds do not cancel. In valence-bond theory, we assume that bonds form when unpaired electrons in valence-shell atomic orbitals pair; the atomic orbitals overlap end to end to form -bonds or side by side to form -bonds. The promotion of electrons will occur if, overall, it leads to a lowering of energy by permitting the formation of more bonds.
