Resonance in SO4

[clairedisc3b]

Hi, Today in class we learnt that the resonant structure of SO4 (2-) is when S has 2 double bonds and 2 single bonds, calculated using the formal charge. Why isnt having 4 double bonds more stable since the FC will be 0 for all of the O atoms?

[Christian Fulinara 3H]

Sulfur is not able to hold 16 valence electrons in its valence shell.

[PranithaPrasad]

Also I think we want the central atom to have a formal charge be zero, or at least as close to 0 as it can get. If we made all the oxygen atoms have a formal charge of 0, we would have the total formal charge of -2, but the structure would be less stable since the formal charge of sulfur would become -2.

[clairedisc3b]

So the most important thing is to make sure the FC of the central atom is as close to 0 as possible?

[Christina Cen 2J]

I think the goal is the have the formal charge of all atoms to be as low as possible but having 4 double bonds for S is not possible.

[Clarisse Wikstrom 1H]

The most ideal situation is...
1. Formal charge closest to zero
2. central atom w/o charge
3. charges (if any) distributed as evenly as possible among atoms (2- vs 1- and 1-)
Hope this helps!