Question #aa9b7

1 Answer
Dec 7, 2016

#OCS# is polar
#XeF_4# is not polar
#NH_3# is most definitely polar


When trying to determine the polarity of a chemical species its important to consider the molecular and electronic geometry of the species and try to map out where exactly the the dipole moment should be (if it exists).

Consider the graphics below:

You could draw a lewis structure for #NH_3# like this:
enter image source here

But it's important to realize that it actually looks much more like this geometrically:
enter image source here

With the lone pair on the central species N significantly affecting the polarity of the molecule.

The nitrogen within the molecule is more electronegative and the valence electron about the species will be closer to it than to the hydrogen.

We sometimes write this as #delta^-# for #N# and #delta^+# for H.

Here are the simple lewis structure for the other species:

enter image source here

enter image source here

I recommend to look at their structure and try to think about the polarity of the species.