textbook problems

[Monica Soliman 3F]

for the textbook problems, why are all the answers in resonance have a lot of formal charges? I thought the best resonance is one that has the least possible charge. ِِِExample for q.2.7?

[Faith St Amant 3D]

The most favorable resonance structure is the structure with the smallest magnitude of formal charge, and with the negative charge on the most electronegative atom. Sometimes, like in 2.7, all of the resonance structures for the molecule have different formal charges within the molecule. To choose the molecule that is most stable, just look for which one has the least formal charges in the most electronically favorable fashion. Hope this helps!