01:160:159 Lecture Notes - Lecture 18: Lone Pair, Steric Number, Vsepr Theory
Document Summary
Chapter 10 the shapes of molecules: vsepr theory valence shell electron pair repulsion theory. Dictates the shape based on the number of bonds and lone pairs a compound has. Steps: draw lewis structure, determine steric number (steric number: number of atoms bonded to central atom, count lone pairs, determine shape. The effect of lone pairs: lone pairs repel bonding pairs more strongly than the bonding pairs do each other, formal charge and resonance structures. Formal charge is the charge an individual atom would have if all the electrons were shared evenly according to their bonds. You want the formal charge to be as close to zero as possible. Formal charge = (number of valence e-) (number of shared e- + number of unshared e-) Resonance structures are used to represent all possible orientations of a molecule. They actually exist as an average of all the resonance structures because electrons move so quickly through the molecule: molecular shape and molecular polarity.
