How does charge affect a lewis structure?

1 Answer
Jan 22, 2018

Well, a Lewis structure should reflect our idea of formal charge....


And let us take nitrite ion as an exemplar.....we gots #NO_2^(-)#, for which we have to distribute......

#5+2xx6+1=18*"valence electrons"#:

And either resonance isomer does distribute the nine electron pairs...

Nitrite ion has a formal negative charge.....given the diagram, the left hand structure has a oxygen atom with with 7 valence electrons, i.e. with the two inner core electrons, there are 9 electrons associated with this atom, and thus a formal negative charge, i.e. for oxygen #Z=8#.

On the other hand, the central nitrogen formally owns 5 valence electrons, and with the two inner core electrons, has 7 electrons to balance the 7 nuclear charges....and thus nitrogen is represented as a neutral species.