Question

Compare the structures of SO3 to PF3 and explain why they have different molecular shapes?

(when comparing two objects, you should discuss both objects, you should discuss both and mention both their similarities and differences and explain the reason for the differences)

Answer 1

See below.

Explanation:

`SO_3` is a molecule that has a Lewis structure like this:

`PF_3` has this Lewis structure:

Similarities:

• Both are bonded to 3 atoms.

• Both don't have any resonance structures (no double bonds in `PF_3` and nowhere else to put the double bonds in `SO_3`)

Differences:

• The central atom in `PF_3` has 1 lone pair of electrons, while the central atom in `SO_3` has no lone pairs.

• `SO_3` violates the octet rule, while `PF_3` obeys it (3 single bonds around P and 1 lone pair = 8 total electrons, while 3 double bonds around S is 12 total electrons).

• `PF_3` has a trigonal pyramidal molecular geometry, compared to `SO_3` having a trigonal planar molecular geometry (P is bonded to three atoms and has 1 lone pair, while S is bonded to 3 atoms and has no lone pairs) (see picture below).

• `PF_3` will be a polar molecule and `SO_3` will be a nonpolar molecule (because the structure of `PF_3` is not symmetrical and `SO_3` is symmetrical, meaning the individual dipole moments of each bond will be 'canceled out' in `SO_3`, but not in `PF_3`, leaving a net dipole moment (polarity) in `PF_3.`

I hope that's enough and that this helped!