Objectives VESPR Theory Continue with Lewis dot Drawings

Molecular Shape Introduction The shape of a molecule determines many of its physical and chemical properties.

I. VSEPR Theory Valence Shell Electron Pair Repulsion Theory Theory that predicts shape of molecule which is important because the shape determines whether or not molecules can get close enough to react. Theory is based on minimizing outer level electron repulsions.

Steps for predicting molecular structure 1) draw the Lewis structure 2) count the shared sites ( include lone pairs; also a double bond is counted as one site and so is a triple bond) and the lone pairs around the central atom. The add the two together to get the total 3) then refer to Table we are about to make

PictureNameDot Struc.# of Non-bonding# of BondedBond AngleExample LinearN2N2 2 bonds0 electrons4 or more electrons 180CO 2 Trigonal Planar 3 bonds0 electrons6 electrons120BCl 3 Tetrahedr al 4 bonds0 electrons8 electrons109.5CH 4 Trigonal Pyramidal 3 bonds1 lone pairs 2 electrons 6 electrons107.3PH 3 Bent2 bonds2 lone pairs 4 electrons 104.5H2OH2O

More Practice

Electronegativity and Polarity You know that the type of bond that forms when two elements react depends on which elements are involved. In general, we have said that an ionic compound forms from a metal and nonmetal and a covalent compound forms from two nonmetals. However, there are exceptions to these rules.

Ionic Polar Covalent Nonpolar Covalent Let’s look at H and O, Na and Cl and H2. Molecular Polarity Polar molecules are generally the result of polar bonds not all polar bonds produce polar molecules To determine if a molecule is polar or not: 1. draw the lewis dot structure 2. in general, if there are lone pairs around the atom, then the molecule is polar because lone pairs occupy more space. 3. if the molecule is not bonded to atoms that are all the same, then the molecular is polar