AA: Nitric acid and nitrate ions

Nitrate(V) ion, NO32−

(Nitrate ion)

The first diagram is a dot-cross diagram or a Lewis Structure as they are sometimes called.  It shows the individual electrons involved in bonding.  The second image shows more clearly whether bonds are single, double or dative covalent.

These images are called resonance structures.  They show that two of the electrons in the double bond are delocalised over the whole ion.

The delocalised electrons are shown as dashed lines in these structures.  The first image shows the charge on the ion is −1 and the second shows the bond angles in the planar ion.



Nitrate(III) ion, NO2

(Nitrite ion)


Nitrogen dioxide, NO2

(Nitrogen[IV] oxide)

NO2 is actually a radical (having an unfilled octet). Therefore, it doesn't really have a proper Lewis structure. Because of the unfilled octet, NO2 has a tendency to dimerize to N2O4 in an attempt to attain a fully filled octet around each nitrogen atom.  Oxidation state of N: +4


The reaction of copper metal with nitric acid:

Cu + 2 HNO3 + 2 H+ → Cu2+ + 2 NO2 + 2 H2O

Some of the nitrate ions form copper(II) nitrate, Cu(NO3)2.





4 H+(aq)


2 NO3-(aq)



2 NO2(g)


+ 2 H2O(l)















Cu2+(aq) + 4 NH3(aq) → Cu(NH3)42+(aq)

Concentrated nitric acid is a very strong oxidising agent.

It is capable of reacting with the noble metals such as copper or silver.