Sciencemadness Discussion Board

Bonding in the nitrate ion

blip - 28-7-2003 at 19:36

This question's been bugging me for a few days: Is the lone pair on the nitrogen atom in the nitrate ion involved in (coordinate covalent) bonding to the third oxygen atom? Like:<tt>
&nbsp;-&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-
|··&nbsp;&nbsp;&nbsp;&nbsp;··|&nbsp;-1
|&nbsp;O::N:O:|
|··&nbsp;&nbsp;·&nbsp;··|
|&nbsp;&nbsp;&nbsp;&nbsp;·&nbsp;&nbsp;&nbsp;|
|&nbsp;&nbsp;&nbsp;:O:&nbsp;&nbsp;|
&nbsp;-&nbsp;&nbsp;&nbsp;··&nbsp;-</tt>

Where the rightmost oxygen atom is the one doing the coordinate covalent bonding. Sorry about the bad ASCII drawing. :( I haven't been able to find any info about this.

chemoleo - 28-7-2003 at 20:25

looks ok to me. you will have an equilibrium of three states, however, all of which are identical - i.e. the extra negative charge on the right most oxygen goes to the top and bottom ones -> electron delocalisation, making the whole thing more stable.

blip - 28-7-2003 at 23:53

Actually it was the bottom oxygen atom that's supposed to be negatively charged, see the single bond there? :P The rightmost oxygen atom has no charge, it's the one that coordinately covalently bonded to the nitrogen via its lone pair. I already knew there was that bonding thingy going on where all bonds are identical and the whole molecule carries that one charge, just it would be a <i><b>real</b></i> pain to draw a resonance diagram in ASCII. Btw, my graphical pictures would look so much worse! :o

vulture - 29-7-2003 at 03:20

I made a little drawing for you.
It also shows why nitric acid is a strong acid, because the nitrate ion has more resonance possibilities.

Acidic and basic behaviour can almost always be explained by resonance.

NO3 .gif - 2kB

blip - 29-7-2003 at 20:01

Thanks for the pic, even though I've seen it before.
Quote:

Acidic and basic behaviour can almost always be explained by resonance.

Hmm, I didn't know that. :) Cool.