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)

1 Answer
Nov 29, 2017

See below.

Explanation:

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

http://www.chem.ucla.edu/~harding/IGOC/S/sulfur_trioxide.htmlhttp://www.chem.ucla.edu/~harding/IGOC/S/sulfur_trioxide.html

PF_3 has this Lewis structure:

http://pixshark.com/pf3-lewis-structure.htmhttp://pixshark.com/pf3-lewis-structure.htm

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.

http://hootcampapchemistry.wikispaces.com/Bonding?responseToken=76cad330384c2794b05fa609eea382fehttp://hootcampapchemistry.wikispaces.com/Bonding?responseToken=76cad330384c2794b05fa609eea382fe

I hope that's enough and that this helped!