1. Section 2: Molecular Geometry

2.  Forces draw the atoms closer together. These forces of attraction are called Intermolecular Forces.  Multiple Bonds – occur in covalent bonds when atoms share more than one electron.  Double Bond – atoms share 2 electrons  Triple Bond – atoms share 3 electrons

3.  The more bonds between 2 atoms, the stronger the bond.  The more bonds between atoms, the shorter the length of the bonds become Bond Strength  Single Bond < Double Bond < Triple Bond Bond Length  Single Bond > Double Bond > Triple Bond

4.  States that repulsion between the sets of valence electrons causes sets to be placed as far apart as possible.  Electrons have the same charge, which causes them to repel each other as far as possible  Leads to unique angles between atoms in the molecule. ▪ Bond Angle – Angle made between two adjacent atoms in a molecule

5.  Bending of molecules leads to one of these molecular shapes…  Linear  Trigonal-planar  Tetrahedral  Bent  Trigonal-pyramidal  Trigonal-bipyramidal  Octahedral

7.  A molecule may be polar or non-polar, just like the individual covalent bonds  You must consider 2 things when determining polarity of a molecule ▪ 1) The polarity of the individual bonds in the molecule ▪ 2) The shape or geometry of the molecule

8.  There are 3 possible outcomes  If all bonds are non-polar, then the whole molecule is non-polar regardless of its shape  If there is symmetry in the molecule so that the polarity of the bonds cancels out, then the molecule is non-polar ▪ O=C=O The carbon-oxygen bond is a polar bond, but because they are exactly opposed to each other, the molecule is overall non-polar

9.  If there are polar bonds but there is no symmetry such that they cancel each other out, the overall molecule is polar ▪ Water is a typical example of this. The two O-H bonds are oriented in a V-shape, and so the don't cancel out ▪ Similarly, CH3Cl is also polar. It is the same shape as CCl4 (see above), but now it doesn't have the same symmetry because there is only one C-Cl bond and the bonds don't cancel out anymore