How to rationalise the resonance structures of nitrogen dioxide?

The following image depicts resonance in $\ce{NO2}$ molecule:


[![resonance in NO2](https://i.stack.imgur.com/NbmGB.jpg)](https://i.stack.imgur.com/NbmGB.jpg)


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](https://chemistry.stackexchange.com/q/9448/4945), 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:


[![enter image description here](https://i.stack.imgur.com/xwRnd.jpg)](https://i.stack.imgur.com/xwRnd.jpg)


But, this isn't the case here. Why?


