praseodym
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Azide anion
I was just thinking of how to draw the bonding present in an azide anion. A search on wikipedia shows that its 2 double bonds connecting 2 N- ions
with one N+ ion in the centre. Hence, giving the azide anion its resulting charge of -1. The bonding shown by wikipedia shows this:
N-=N+=N-
However, what i cannot understand is that why is it 2 double bonds between each N- ions and the N+ ion but not a triple bond connecting one N atom to
the centre N atom and a dative bond connecting a N- ion with the centre N atom since both give a stable octet structure to each N atom. Moreover, both
also give an effective charge of -1 to the azide anion. Therefore, what is the reason for the way the N atoms are bonded in the azide anion? Could it
be due to the more symmetrical pattern, resulting in better defined molecular geometry and electron-pair geometry? Or is it that there is less
electron repulsion since the electron density regions are more separated?
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Quibbler
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Drawing lines to represent bonds between capital letters representing atoms is only a crude representation of what is actually taking place. It's
actually surprising it works so well. MO calculations suggest that the two outer N atoms have half a negative charge and the central N is uncharged.
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guy
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The charge on each atom of the azide ion is actually -1/3. The electrons are delocalized throughout the whole ion. MO theory does a better job of
explaning resonance structures such as this.
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praseodym
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So how does the delocalised electons ensure that each atom of the azide anion is -1/3? As in, how does it work? Btw can u expand more on the MO
theory?
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Nerro
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Molecular orbital theory is a tad complex to explain here  It basically states the
electrons in a molecule are spread over new molecular orbitals rather than discreet atomic orbitals of the constituent atoms.
The charge is spread out by means of resonance which means the 1- charge is spread over three N's which means the charge is -1/3 rather than -1 on a
single N.
Octet theory also explains this.
5 + 5 + 5 + 1 = 16
3 * 8 = 24
24 - 16 = 8
8 / 2 = 4
So you need four bonds in this molecule. [N=N=N]<sup>-</sup> 
[Edited on Fri/Mar/2006 by Nerro]
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