What is the Lewis structure for HNO3?

The Lewis structure for HNO₃, or nitric acid, showcases the arrangement of electrons around the atoms in the molecule.

First, we need to count the total number of valence electrons available. Hydrogen (H) has 1 valence electron, nitrogen (N) has 5, and each oxygen (O) has 6. With one hydrogen, one nitrogen, and three oxygen atoms, the total is:

• 1 (H) + 5 (N) + 3 × 6 (O) = 1 + 5 + 18 = 24 valence electrons

In the Lewis structure of HNO₃, nitrogen is the central atom. It forms one double bond with one oxygen atom and one single bond with another oxygen atom which, in turn, is bonded to a hydrogen atom. The three atoms of oxygen are arranged around the nitrogen atom, with one oxygen forming a double bond.

This structure can be represented as follows :

     O
     ||
H - N - O
        |
         O

In this representation:

• The double bond between N and one O means they share four electrons.
• The single bond between N and the other O means they share two electrons.
• The single bond O is then bonded to H.
• The remaining valence electrons are placed on the oxygen atoms to satisfy the octet rule.

Overall, HNO₃ is a polar molecule due to the difference in electronegativity between nitrogen and oxygen, creating a dipole moment. This structure not only satisfies the octet rule for each atom (with hydrogen only needing two electrons) but also accurately reflects the functional groups present in nitric acid.