\ HNO3 (Nitric Acid) Lewis Structure

HNO3 (Nitric acid) Lewis Structure

HNO3 (Nitric acid) lewis stricture is drawn step by step by using valence electrons of each element. In the lewis structure of nitric acid, there is a +1 charge on nitrogen atom and one double bond between nitrogen and one oxygen atom.

Lewis structure of nitric acid

There is a N=O bond in nitric acid lewis structure. There are no lone pairs on nitrogen atom and also there are charges on one oxygen atom and nitrogen atom. You can see those signs in the following figure.

HNO3 lewis structure

Steps of drawing lewis structure of HNO3

There are some steps to follow to draw the HNO3 lewis structure and those steps are explained in detail in this tutorial.

  1. Find total number of electrons of the valance shells of hydrogen, nitrogen and oxygen atoms
  2. Total electrons pairs
  3. Center atom selection
  4. Put lone pairs on atoms
  5. Mark charges
  6. Check the stability and minimize charges on atoms by converting lone pairs to bonds.

Important: Drawing correct lewis structure is important to draw resonance structures correctly.

Total number of electrons of the valance shells of HNO3 acid

Hydrogen is a group IA element and has one electron in its last shell. Nitrogen is located at group VA and has five electrons in its valence shell. Oxygen is a group VIA element in the periodic table and contains six electrons. Now we know how many electrons are includes in valence shells of each atom.

  • valence electrons given by hydrogen atom = 1
  • valence electrons given by nitrogen atom = 5
  • valence electrons given by oxygen atoms = 6 *3 = 18

  • Total valence electrons = 1 + 5 + 18 = 24

Total valence electrons pairs

Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells

Total electron pairs are determined by dividing the number total valence electrons by two. For, HNO3, Total pairs of electrons are 12 in their valence shells.

Center atom of HNO3

To be the center atom, ability of having greater valance is important. Then, from hydrogen, nitrogen and oxygen, which atom has the highest valence. Nitrogen can show valence five which is greater than maximum valence of oxygen two. Therefore, nitrogen atom should be the center atom of HNO3.

sketch of HNO3

Lone pairs on atoms

After determining the center atom and sketch of HNO3, we should start to mark lone pairs on atoms.

  • There are already three N-O bonds and one O-H in the drawn sketch structure. Therefore number of total bonds in the sketch is four. Now only eight (12-4) valence electrons pairs are remaining to mark on atoms.
  • First, mark those remaining eight valence electrons pairs as lone pairs in outside atoms (on oxygen atoms). Because oxygen atom follow octal rule (oxygen atom cannot keep more than eight electrons in its valence shell) be careful to protect it.
  • After marking lone pairs on oxygen atoms, there is no more lone pairs to mark on nitrogen atom (That is not a problem in steps of drawing lewis structures!)
mark valence electrons in HNO3

Charges on atoms

After, marking electron pairs on atoms, we should mark charges of each atom. Two oxygen atoms will get a -1 charge and nitrogen atom get a +2 charge.

mark charges on atoms in nitric acid

Check the stability and minimize charges on atoms by converting lone pairs to bonds

Best lewis structure should have low charges on atoms.

  • Oxygen atoms should hold negative charges because electronegativity of oxygen is higher than nitrogen. Otherwise, we can say, ability of holding negative charges is great in oxygen atoms than nitrogen atom.
  • The drawn structure is not a stable one because two oxygen atoms and nitrogen atom have charges.
  • Now, we should try to minimize charges by converting lone pair or pairs to bonds. So convert one lone pair of one oxygen atom to make a S-O bond (See the following figure).
  • Now there is a double bond between nitrogen atom and one oxygen atom. Now, there are two single bonds between nitrogen atom and other two oxygen atoms.
reduce charges to obtain best HNO3 lewis structure

In the new structure of HNO3, charges are reduced. Therefore, this is the best lewis structure we can draw for HNO3.


Are there lone pairs on nitrogen atom in HNO3 lewis structure?

There are no lone pairs on nitrogen atom. There are two N-O bonds and one N=O bond. So, there is +1 charge on nitrogen atom.

Are their charges on oxygen atoms?

Two oxygen atoms have charges (-1 for those oxygen atom).

Is HNO2 lewis structure is similar to HNO3

No. Clearly they are different because there is one more oxygen atom in HNO3. Therefore, there should be another bond between nitrogen and that oxygen atom.

Lewis Structures of Molecules