Chapter 9 Notes – Part III
Mr Nelson 2010
Polarity
• But just because a molecule possesses polar bonds does not mean the molecule as a whole will be polar.
Polarity
• There are two ways to tell if a molecule is nonpolar:– Symmetry – perfect symmetry
= nonpolar
– Dipoles moments – if the dipoles ‘cancel out’ the molecule is nonpolar
Examples
• Draw the Lewis Dot Structure for:– HCl
– CCl4
Bonding & Lone Pairs
• Electron pairs that are shared are called bonding pairs
• Electron pairs that are not bonded or shared are called lone or unshared pairs
Steric Number• The total electron pairs
around the central atom is the steric number.
• Double or triple bonds count as one steric number (electron domain).
• The central atom has a steric number of four.
Determining the shape of molecules
VSEPR (not the Bond girl Vesper)
• VSEPR: Valence Shell Electron Pair Repulsion
– Electron pairs will arrange so they are as far apart as possible. ALL HAVE NEGATIVE CHARGES
– ALL e- pairs determine the shape, bonded or not, but ONLY bonded pairs determine the name of the shape.
