posted by Anonymous .
which of the following molecules is polar?
You have to draw Lewis Dot structures and than use 1 of two approaches. The first is The vector addition approach, which is most helpful for smaller molecules. The 2nd approach is the center of charge approach, and you look to see where your negatives and positives are on your lewis dot structure. If your negative is way up top and your positives are way down low, the structure is non polar.
To do these properly you need to draw the Lewis electron dot structure and assign a shape to them. The shapes that are symmetrical are polar. The symmetrical shapes are not polar unless one of the binding sites is a different atom than then others. (For example, SF6 is octahedral and non-polar because it is symmetrical while SF5Cl is not symmetrical and is polar.)
NO2 is angular with an uneven number of electrons and is polar.
CO2 is linear and not polar.
BF3 is trigonal planar and not polar.
SF6 is Octahedral and is not polar.
CCl4 is tetrahedral and is not polar.
dot and cross diagram of a molecule of HOCL