Which of the following molecules is polar?

Question

1. CH4
2. BH3
3. NH3
4. CF4
5. H2

Answer 1

To be polar, molecules must have the following:
1. There must be a difference in electronegativity between the central element and the binding element(s).
2. The molecules must NOT be symmetrical.
CH4, for example, has a small difference in EN between C and H, but it is tetrahedral which makes it symmetrical and the CH4 molecule as a whole has no dipole moment.