How do we know which lewis structure to use?

[205743684]

Hi, I was wondering if anyone could summarize how we know which Lewis structure we would know to use based of simply getting the name of a compound...? I watched all the lectures but feel like there are always exceptions to what was discussed in previous examples. Is there a step by step process of elimination to figure out how we should proceed to draw it or just learn the exceptions very well?

[Kaleigh Olla 1L]

Based on the lectures in class, I think the steps are:
1. Count the electrons (accounting for cation and anions)
2. put element with least electronegativity in the center
3. place other elements symmetrically around the center
4. make single bonds and add double/triple bonds as necessary
5. count electrons and make sure they add up to the amount of electrons in the compound

[405716590]

I guess the exceptions would include things like the formal charge, so we knew that the one structure we went over in class used two double bonds and two singles instead of four singles because the formal charges were more stable that way. So i would also check the formal charge of the individual atoms.

[Matthew Li 1B]

always try to minimize formal charge and also put the atom with the lower ionization energy in the center

[Trisha Nagin]

The atom with the lowest ionization energy usually goes in the center. Just check and try to minimize the formal charge of the atoms.