Resonance

[Nathan Mariano 2G]

How do you determine which structure is the most stable? For example, why does the resonance structure of SO4^2- prefer to form a two double bond with two oxygen instead of forming a double bond with one sulfur and one oxygen? Sulfur and Oxygen both have the same amount of valence electrons.

[Samantha Ito 2E]

Check the formal charges of the atoms when determining the most stable structure. Typically, the structure with the most formal charges of zero on atoms is the more stable Lewis structure. When there must be positive or negative formal charges on various atoms, the most stable structures generally have negative formal charges on the more electronegative atoms.

[Nicolette_Canlian_2L]

In the case of the sulfate ion, sulfur and the oxygens that are double-bonded to the sulfur will have formal charges of zero. The oxygens that are single-bonded to the sulfur will each have a formal charge of negative one, adding up to negative two. This contributes to the sulfate ion's charge of negative 2.

[Ibrahim Malik 1H]

The most stable structure would be the lewis structure with the least amount of charges on it, and has as many formal charges of 0 as possible.

[klarratt2]

You have to check the formal charges of each of the molecules. Oxygen is more stable when it has a double bond, so the SO4- molecule will prefer that structure.