Hi I wonder if you could help me with the following multiple choice questions:  Which of the following does not have a dipole moment a) H20 b)NH3 c)CO2 D)SF4 E)BRCL5 Are we just suppose to know that the answer is CO2 or is there some simple way of working it out?  The Lewis structure of PCl3 indicates four regions of high electron density around the phosphorus atom: one lone pair and three single bonds. What is the shape of the PCl3 molecule? [a] Tetrahedral (b)trigonal pyramidal c)trigonal planar e) T-shape How do we know that the answer is a trigonal pyramidal shape? 3] Similar sort of question - what is the molecular structure of IF6+ (a) octahedral (b) trigonal bypyramidal (c) square pyramidal (d) trigonal planer In this case the number 6 denotes that it is an octahedral but often the answer is not so straightforward when non bonding pairs are concerned. How do we know if there are non bonding pairs?