Lewis structure for NO+

Question

I need to know two things.

First, NO+ lewis strucutre is usually drawn with a triple bond, and the + charge is put with a bracket to both ions. Why is that? Isn't O the only atom that should get it?

 

Secondly, why can't we draw it with a double bond inbetween, with a + charge on N atom?

Answer 1

Hello Yoshani,

 

We bracket the ion and assign it a "collective" positive charge because the small size of the ion will leave that positive charge flickering about the entire molecule: it would be erroneous to assign that charge to a specific place. This phenomenon is called "resonance."

 

The structure you proposed is a resonance (i.e. plausibly alternative) structure, with oxygen taking two lone pairs, leaving nitrogen with a +1 charge. This is not how we'd draw up the molecule, since we love octets around all the atoms, but it's a valid resonance structure: the ion has this character at times, its structure oscillating back and forth between the two structures quicker than you can imagine. The + charge favors the oxygen side,though, so we call that side the "reactive end" of the molecule.

 

Attack by a nucleophilic molecule (something electronegative, with a ^- charge, for example) will usually be on the oxygen side, since that is where the positive charge spends most of its time.

Answer 2

I think you are confusing the formal charge of oxygen (which in the case of this Lewis structure would be +1) with the actual charge on the atoms. Neither the nitrogen nor the oxygen has the entire positive charge. The positive charge is distributed across the whole molecule (which is why the molecule is put in brackets with the charge corresponding to the whole thing).

 

The only way I can draw the Lewis structure with a double bond and a formal charge of +1 on the nitrogen (and 0 on the oxygen) violates the octet rule. That structure (though it contains all 10 valence electrons that you distribute between the two atoms) only has 6 valence electrons on the nitrogen.

 

Hope this helps!