# Why is N(OH)_3 unknown?

Oct 2, 2016

Refer to the explanation.

#### Explanation:

The nitrate ion, ${\text{NO"_3}}^{-}$. It is a polyatomic anion that has an overall charge of $\text{1"^(-)}$. The nitrate anion is considered a single ion. The hydrogen cation, $\text{H"^+}$ has a charge of $\text{1"^+}$. Since nitric acid is a neutral compound, it is composed of one hydrogen cation and one nitrate anion.

$\text{NO"_3^(-)"+H"^+}$$\rightarrow$$\text{HNO"_3}$

Note: carbonic acid is composed of the carbonate anion, ${\text{CO"_3}}^{2 -}$, and the hydrogen cation. As with the nitrate anion, the carbonate anion is a polyatomic anion that has an overall charge of $\text{2"^(-)}$, and is also considered a single ion. Since the carbonate anion has a charge of $\text{2"^(-)}$, it will need to be combined with two $\text{H"^(+)}$ cations to make the neutral compound carbonic acid.

$\text{CO"_3^(2-)"+ 2H"^(+)}$$\rightarrow$$\text{H"_2"NO"_3}$

The following is a list of polyatomic ions with their names, formulas, and charges.
http://www.chalkbored.com/lessons/common-polyatomic-ions.pdf

Oct 2, 2016

To address your question, I think you ask why a molecule such as $N {\left(O H\right)}_{3}$ is not observed?

#### Explanation:

Trihydroxylamine, $N {\left(O H\right)}_{3}$, is probably observed spectroscopically. However, this species is probably unstable with respect to hydroxylamine, which further disproportionates to nitrous and nitric oxide:

$N {\left(O H\right)}_{3} \rightarrow H O - N = O + {H}_{2} O$

$2 H O - N = O \rightarrow N {O}_{2} + N O + {H}_{2} O$

Just to add that for the Lewis structure of nitrate anion, O=N^+(−O)_2^(-), every atom is associated with 8 electrons. However, for each mesomer, there are 3 formal charges assigned. Two of these are negative charges and are formally oxygen based, and the nitrogen is quaternized and bears a formal positive charge. Of course the overall charge is still −1, as required.

For the neutral parent acid, O=N^+(−O^−)(−OH), there are thus 2 formal charges assigned.