CHEM 101 Lecture Notes - Lecture 27: Trigonal Planar Molecular Geometry, Relative Direction, Steric Number
Document Summary
As discussed in class, the vsepr geometry of a molecule can be used in combination with its bond dipole vectors to predict if the molecule will be polar or non-polar. It is a matter of being able to picture the vector tug-of-war among the molecule s bond dipoles to see if there is cancellation (non-polar molecule) or not (polar molecule). It was easy to demonstrate for the linear (steric number (sn) = 2) case. Herein we want to demonstrate it for the less obvious trigonal planar (sn = 3) and tetrahedral (sn = 4) cases. Hopefully, you will then believe what was stated: Since we are dealing with a vector quantity, we will address the two issues, magnitude (length) and direction (geometry), separately: magnitude: bond dipoles of equal length . Recall, the length of the bond dipole vector ( bond) depends on two (2) factors for the polar a-b bond:
