The following image depicts resonance in $\ce{NO2}$ molecule:
I don't know if it is obvious or not, but I'm puzzled by this structure. I've read about the structure of the $\ce{NO2}$ compound, but it wasn't related.
In the first structure, nitrogen is having a single electron with a positive charge, and oxygen is having a negative charge. So, that means nitrogen has donated a single electron to Oxygen, without forming a bond. I know it can be possible, but I couldn't understand how it happens.
Also, I thought that nitrogen donates a lone pair to oxygen, as it can have a maximum co-valency of 4. As in the following image:
But, this isn't the case here. Why?