[gebbissimo]

Hi there,

I would like to know the REASONS behind why the Lewis structures for NO2 and Ozone are as they are.

No2:
At first sight I drew NO2 without the formal charges, as in this image:http://www.madsci.org/posts/archives/2000-02/951452623.Ch.2.gif

But apparently, in the more important structure, an electron is 'transformed' from the Nitrogen Atom to one of the Oxygen atoms. Why is that so? (My guess would be because of the higher electron affinity of Oxygen).



Ozone:
Again, the first time I drew Ozone, I used two lonely electrons at each of the Oxygen ends. But again, an electron transfers from the center atom to one of the ends. Why?  Is it because of the fact, that radicals (lonely electrons) are just too energetically unfavorable?

Second question concerning ozone: Why don't they just form a triangle? No formal charges, no radicals, seems perfect to me. Only idea against that configuration would be too close proximity and thus pauli or Coulomb-repulsion. But I think that's a weak argument.


Thank you very much in advance! I couldn't find answers to these questions in the web, so I'd appreciate your time effort a lot.
Cheers

[majorjp]

The reason in both cases, in respect to nitrogen dioxide and ozone, both structure are formed as they are the most stable formations for the molecule due to resonance.
In nitrogen dioxide the electron can be tranferred to the oxygen due to oxygen's higher electronegativity. The most popular way to draw nitrogen dioxide is in it's hybridized form. It should be noted that nitrogen dioxide only exist in equilibrium with dinitrogen tetraoxide.
As for ozone the drawing is showing the two absolute possible configurations, however the hybrid structure reflects more accurately the natural structure of ozone. The reason for showing the negative charges always on the terminal oxygens is to reflect the resonance stability of molecule.
The reason the ozone molecule doesn't take a cyclic structure is due to the steric strain on the bonds at that bond angle, it is extremely unstable and therefore extremely unfavorable.