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Which is the correct structure of $\ce{NO2}$? While searching the internet I found out that

  1. $\ce{NO2}$ have a coordinate and two covalent bonds. $\ce{N}$ will have a positive charge. $\ce{O}$ (coordinate bond) will have a negative charge (this is the part which I don't understand. As $\ce{O}$'s octet is complete, why will it have a negative charge?)

  2. $\ce{NO2}$ came from $\ce{HNO2}$ that's from $\ce{O}$ have a negative charge. but in this molecule, there is no $\ce{O}$ with coordinate bond.

  3. In one molecule $\ce{N}$ have one electron and positive charge and in other two electrons and no charge?

Mithoron
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Bhavay
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  • Are you asking about the Lewis structure together with the formal charges? You can have a non-zero formal charge for atoms that have an octet - the way the electrons are counted is different for those two concepts. It would help if you edited your answer to show the Lewis structures you are talking about. As written, I'm not even sure if you mean $\ce{NO2}$ or $\ce{NO2-}$. – Karsten May 10 '19 at 19:28

1 Answers1

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$\ce{NO2}$ is a free radical. Its resonance structures are as follows:

resonance

Unsurprisingly, $\ce{NO2}$ reacts readily with a variety of substances, including itself at low temperatures to form $\ce{N2O4}$.

enter image description here

From Wikipedia:

enter image description here

Nitrogen dioxide at −196°C, 0°C, 23°C, 35°C, and 50°C. ($\ce{NO2}$) converts to the colorless dinitrogen tetroxide ($\ce{N2O4}$) at low temperatures, and reverts to $\ce{NO2}$ at higher temperatures.

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ringo
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  • where did this minus sign came from? – Bhavay May 09 '19 at 23:27
  • @Bhavay are you referring to the oxygen? It is just the formal charge on it for that resonance structure. There is no true negative charge on the oxygens. It is a neutral molecule. This may help. – ringo May 09 '19 at 23:29
  • n will have a formal charge of +1? right – Bhavay May 09 '19 at 23:30
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    The molecule is neutral, it can't have an unbalanced negative formal charge. As is the nitrogen should have a positive formal charge (seven valence electrons). – orthocresol May 09 '19 at 23:31
  • what about hno2 then .is no2- from hno2 and no2 radicle same ? – Bhavay May 09 '19 at 23:35
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    @Bhavay No, $\ce{NO_2^-}$ has one additional electron compared to $\ce{^\cdot NO_2}$. They're not the same. – hBy2Py May 09 '19 at 23:37
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    Yes, nitrogen has five Valence electrons (@orthocresol seven total). Please count again, because I only see four electrons around nitrogen in either resonance structure you have drawn. A (neutral) molecule can never have an unbalanced formal charge. – Martin - マーチン May 09 '19 at 23:42
  • @ orthocresol @Martin-マーチン thank you for pointing that out. I was a little too hasty in making my drawings. – ringo May 09 '19 at 23:49
  • The ONO bond angle is $\approx 134$ degrees and NO bond length $120$ pm. EPR studies show that the unpaired electron is in a $\sigma$ rather than $\pi$ orbital on the N atom, (i.e in an sp$^2$ hybrid orbital), as shown in the middle and left resonance structures in the figure. Walsh diagrams explain this also. – porphyrin Oct 11 '20 at 11:03