Formal Charge Exceptions

[Kimberly 1H]

A formal charge of 0 indicates a low energy structure, however the textbook also states that in some cases, the structure with the lowest formal charge is not the most likely. What are some factors that may contribute to this?

[Ricky Ma DIS 4E]

Sometimes not every formal charge all add up to 0. In cases where it is an ion, the formal charges have to add up to the charge of the given ion.

ex. Sc2+
the overall formal charge will always be 2+, never 0.

[Dimitri Speron 1C]

There are also exceptions based on what the central atom is and such. For example, if resonance is possible, then the structure will always have resonance because resonance structures are lower energy than non-resonance structures.