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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?

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  • $\begingroup$ 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 $\ce{NO2-}$. $\endgroup$
    – Karsten ♦
    May 10, 2019 at 19:28

1 Answer 1

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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 $\ce{N2O4}$.

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From Wikipedia:

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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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  • $\begingroup$ where did this minus sign came from? $\endgroup$
    – Bhavay
    May 9, 2019 at 23:27
  • $\begingroup$ @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. $\endgroup$
    – ringo
    May 9, 2019 at 23:29
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    $\begingroup$ 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). $\endgroup$
    – orthocresol
    May 9, 2019 at 23:31
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    $\begingroup$ @Bhavay No, $\ce{NO_2^-}$ has one additional electron compared to $\ce{^\cdot NO_2}$. They're not the same. $\endgroup$
    – hBy2Py
    May 9, 2019 at 23:37
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    $\begingroup$ 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. $\endgroup$
    – Martin - マーチン ♦
    May 9, 2019 at 23:42

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