Question

Which statement is true about BF3, a nonpolar molecule?


It has nonpolar bonds and a symmetrical structure.

It has nonpolar bonds and an asymmetrical structure.

It has polar bonds and a symmetrical structure.

It has polar bonds and an asymmetrical structure.

It has ionic bonds and symmetrical structure.

Answer 1

BF3 has 120 degrees of speration of B to each F atom.
The structure is symmetric.
Take note that for a compound to be polar, the difference in polarity between the atoms has to be greater than 0.4. For instance for each B-F bond, there in polarity because the difference in electronegativies between F and B is 4.0-2.0=2.0 respectively.
Therefore, the bonds are polar.

Answer 2

From my understanding, If you notice boron has no lone pair electrons, and three atoms bonded, so it's shape will be trigonal planar, and it's bond angle will be 120 degrees, note that the presence of lone pairs cause the bond angle to decrease. Now for the bonds, one would say that they are polar because there is an electronegativity difference between Florine and bromine, if you look those numbers up and that's a great enough electronegativity difference to account for its polarity. However, you also need to take into account the shape, which is trigonal planar, along with the dipoles. Because BF3 is symmetrical and trigonal planar If you draw it out then you'll find the dipoles cancel out, making it a non polar molecule.