Question

I'm trying to find if potassium nitrate is polar or non-polar by using the electronegativity scale. Can someone check my work?

Electronegativity:
potassium: 0.82
nitrogen: 3.04
oxygen: 3.44

=3.44-3.04 =0.82-0.4
=0.4 =0.42
So the final answer is 0.42 and by looking at the electronegativity scale I can see that it is non-polar.

Answer 1

KNO3 is a polar compound. The anions (NO3^- etc) don't have electronegativities listed since they are polyatomic ions. Most of the polyatomic ions are largely covalent bonding. However, it would be more appropriate to use either N or O alone (with K) to calculate the difference in EN of KNO3. Done that way, K at 0.82 and N at 3.04 gives a difference of 2.22 which makes it a polar molecule.