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Lewis Structure of H3PO4 (Phosphoric Acid)

Phosphoric acid (H3PO4) lewis structure is drawn using the concept of total valence electrons. H3PO4 contains three elements phosphorous, oxygen and hydrogen. These elements provide electrons (not all electrons) of last shell to form bonds. In this tutorial, we will learn, how to construct the lewis structure of H3PO4 molecule.



written: Heshan Nipuna, updated: 25/05/2020


Lewis Structure of phosphoric acid molecule

H3PO4 lewis structure

Now, we are going to learn, how to draw this lewis structure of H3PO4 molecule step by step.




Related lewis structures to H3PO4

H3PO2 lewis structure
H3PO3 lewis structure
PO43- lewis structure

Steps of drawing H3PO4 lewis structure

There are several steps to draw H3PO4 lewis structure and they are explained in detail in this tutorial.

  1. Find total number of electrons of the valance shells of phosphorous atom, oxygen atom and hydrogen atoms.
  2. Total electrons pairs in valence shells
  3. Determine center atom from phosphorous atom, oxygen atom and hydrogen atoms.
  4. Put lone pairs on atoms and mark charges on atoms
  5. Stability of lewis structure - Check the stability and minimize charges on atoms by converting lone pairs to bonds to obtain the best lewis structure.


Total number of electrons of the valance shells of phosphorous atom, oxygen atom and hydrogen atoms.




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, H3PO4, there are 32 valence electrons, so total pairs of electrons are 16.



Center atom of H3PO4

For being the center atom, ability of having greater valance is a reason. If we consider each element, maximum valence of hydrogen, oxygen and phosphorous are 1, 2 and 5 respectively. By the experience of drawing lewis structures, we know phosphorous has the greatest chance to be the center atom.


Sketch of H3PO4

H3PO4 sketch

Oxygen atoms are located around the carbon atom and hydrogen atoms have connected to oxygen atoms.




Lone pairs on atoms

mark lone pairs in H3PO4 structure

Charges of atoms in the structure

There is -1 charge on one oxygen atom and there is +1 charge on phosphorous atom. There are no charges on other atoms.

mark charge on oxygen atom as a step of drawing lewis structure of phosphoric acid molecule

Check the stability of drawn structure of H3PO4 and reduce charges on atoms by converting lone pairs to bonds

If possible, you should try to reduce charges on atoms. You can see, that oxygen atom which has -1 charge has three lone pairs can convert its one lone pair to make a bond with phosphorous atom.

reduce charges by converting lone pair to stable the structure of H3PO4

Now there is a double bond between one oxygen atom and phosphorous atom. And there are no charge in any atom. Therefore, this structure should be the lewis structure of H3PO4.



Structure of H3PO4, shape of molecule around phosphorous atom?

There are four σ bonds and no lone pairs around phosphorous atom in the lewis structure of H3PO4 molecule. Therefore total number of VSPER pairs are four. Therefore, shape of molecule around phosphorous atom is tetrahedral.




Questions asked by students.




which is the lewis structure for h3po4?

In the lewis structure of H3PO4, there is one double between phosphorous atom and one oxygeen atom. Rest of all bonds are single bonds. Also, there are no lone pairs on phosphorous atom. There are three O-H bonds which give some acidic charcteristics to H3PO4.



Can I know oxidation number of phosphorous atom of lewis structure of H3PO4

Yes. Oxidation number of phosphorous atom can be calculated from lewis structure of H3PO4.



What is correct about from following statements about the lewis structure of phosphoric acid?

  1. Lewis structure of phosphoric acid contains -1 charge on one oxygen atom and +1 charge on phosphorous atom.
  2. There are three single bonds in the molecule.
  3. There are no charges at any atom.
  4. One hydrogen atom is joint to phosphorous atom and remaining hydrogen atoms are joint to two oxygen atoms.

  • Statement 3 is correct.There is no charges at any atom in the lewis structure of phosphoric acid.



  • how do I obtain lewis structure of phosphoric acid from phosphate ion lewis structure?

    phosphate ion lewis structure containes four oxygen atom. From those four oxygen atoms, there are three oxygen atoms each of them has -1 charge. Three hyrogen atoms are joint to those oxygen atoms to make lewis structure of phosphoric acid.



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