CHM120H5 Lecture Notes - Lecture 13: Trigonal Planar Molecular Geometry, Boron Trichloride, Lone Pair
Document Summary
Midterms to be handed back in tutorials this week. Polyatomic molecules - molecular dipole moment is the sum of the bond dipole vectors. Dipole moment depends on polarity of the bond and shape of the molecule. In co2 and bcl3, the bonds are polar but the linear/trigonal planar shape cancel out the bonds. As the dipole moment increases the intermolecular interaction increases and boiling point increases. Higher dipole moment = higher intermolecular attraction = more energy needed to separate them = higher boiling point. Typical thought process: nf3 has higher electronegativity so has higher dipole moment (nf3 en: 1. 0, nh3 en: 0. 8) Nh3 actually has a higher dipole moment because of the contribution of the lone pair of electrons - in nh3 the ligands and lone pair act together, in the same direction. In nf3 the ligands and lone pair act in opposite directions. Bond angles in a trigonal pyramid is expected to be 109. 5 .
