my teacher told me that polar bonds have a difference in elecronegativities of .4-2.1

Question

is that the only way to find if a bond is polar?

also how would you find out if the MOLECULE is polar or not?
- i think i remember my teacher saying something about dipole moments...

Answer 1

To be polar, a molecule must have both of the following:
a. bonds that are polar AND
b. the molecule must NOT be symmetrical.

Electronegativity is the way to go to determine if a bond is polar.