P2O5 (Phosphorus pentoxide) Lewis Structure

In the lewis structure of P2O5, there are two elements; phosphorus and oxygen. Two phosphorus atoms are linked through an oxygen atom in the lewis structure of phosphorus pentoxide (P2O5). All other oxygen atoms have made double bonds with phosphorus atoms. Steps of the drawing lewis structure of P2O5 molecule are explained in detail in this tutorial.

P2O5 lewis structure

P2O5 lewis structure

In this lewis structure, center oxygen atom has made single bonds with two phosphorus atoms. Each phosphorus atom has made bonds with three oxygen atoms. There are four (P=O) double bonds in this molecule. Also, there are no charges on atoms in P2O5 lewis structure.

Steps of drawing lewis structure of P2O5 lewis structure

When you are trying to draw a lewis structure, there are guidelines to do it. Number of steps can be changed according the complexity of the molecule or ion. Because P2O5 molecule is bit complex molecule, (if you are beginner to lewis structure drawing) you have to be careful when it starts to draw.

steps of drawing lewis structure of P2O5

  1. Find total number of electrons of the valance shells of phosphorus and oxygen atom
  2. Total electrons pairs existing as lone pairs and bonds
  3. Center atom selection
  4. Mark lone pairs on atoms
  5. Mark charges on atoms if there are charges
  6. Check the stability and minimize charges on atoms by converting lone pairs to bonds to obtain best lewis structure.

Total number of electrons of the valance shells of P2O5

There are only two elements in Phosphorus pentoxide; phosphorus and oxygen. Phosphorus is a group VA element in the periodic table and has five electrons in its last shell (valence shell). Oxygen is a group VIA element in the periodic table and contains six electrons in its last shell.

  • valence electrons given by phosphorus atoms = 5 * 2 = 10
  • valence electrons given by oxygen atoms = 6 * 5 = 30

  • Total valence electrons = 10 + 30 = 40

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, P2O5, Total pairs of electrons are twenty in their valence shells.

Selection of center atom of P2O5

To be the center atom in a molecule, ability of having greater valance is important. Then, from oxygen and phosphorus atoms, which atom has the highest valence? We know, it is phosphorus. Maximum valence of phosphorus is five. Oxygen's only valence is two. Therefore, phosphorus atom should be the center atom of P2O5. But, there are two phosphorus atoms. So, we can draw the sketch of P2O5.

sketch of P2O5

Mark lone pairs on atoms of P2O5

After determining the center atom and sketch of P2O5 molecule, we can start to mark lone pairs on atoms. Remember that, there are total of twenty electron pairs to mark as bonds and lone pairs.

  • There are already six bonds in the drawn sketch (six P-O bonds). Now only fourteen (20-6=14) lone pairs are remaining to mark on atoms.
  • Usually, those remaining electron pairs should be started to mark on outside atoms. Then, mark lone pairs on oxygen atoms protecting the octal rule. Four outside oxygen atom will take three lone pairs. Now, twelve electron pairs were marked as lone pairs on outside oxygen atoms. So, now there are only two lone pairs to mark on atoms. Mark those two lone pairs on center oxygen atom.
  • Therefore, there are no lone pairs to mark on phosphorus atoms.
mark lone pairs on atoms in P2O5 lewis structure

Mark charges on atoms

There are charges on each atom. Marking those charges is important to obtain the best lewis structure (most stable). Each outside oxygen atom has -1 charge and each phosphorus atom has +2 charge.

mark charges on atoms on P2O5

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

When there are charges on lot of atoms in a drawn sketch, it is not stable. That means, when there are least charges on atoms, that structure is very much stable. Because, there are charges on most atoms in our current P2O5 structure, that structure is very unstable. Therefore, we can reduce charges of atoms by converting lone pairs to bonds step by step. Those steps are figured below.

reduce charges of atoms to get best P2O5 lewis structure

You can see, in our final structure, there are no charges on any atom. That means, that is the most stable structure and it is the lewis structure of P2O5 .


Lewis Structures of Molecules