This is where most students get tripped up. The POGIL activity usually uses a "Tug-of-War" analogy:
Here’s a summary of the key ideas typically covered in that POGIL: polar and nonpolar molecules pogil answer key
"Why is BF₃ nonpolar but NF₃ polar?" BF₃: trigonal planar, bond dipoles cancel. NF₃: trigonal pyramidal (lone pair on N), dipoles don’t cancel. This is where most students get tripped up