for example, you have a model of AX3, can you tell if BF3 is polar or non-polar? why?

Question

what i mean in model AX3 is, it is a triangular molecules...

Answer 1

The answer is maybe. The BF3 molecule, although composed of highly polar covalent bonds, is nonpolar because of the boron atom's sp2 hybridisation which produce three symmetrical orbitals. Its molecular geometry is trigonal planar. Your AX3 may be a different molecule such a SnCl3-, which is a polar molecule and has molecular geometry of trigonal pyramidal, containing one pair of unshaired electrons. So if you have a physical model to look at, the way to tell if it is polar or non-polar is to look at the alignment of the X molecules. For a non-polar, the X molecules should all be equally spaced with 120 degrees between each of them and they must be flat. By that I mean of you laid it down on a table, the model would be flat on the table and not propped up like a tripod. I hope this helps to answer this.

Answer 2

The AX3 or trigonal planar molecule is Non-polar by definition.
All of the AX3 molecule are non-polar.