PO3– has one phosphorus atom and three oxygen atoms.
In PO3– Lewis structure, there is one double bond and two single bonds around the phosphorus atom, with three oxygen atoms attached to it. The oxygen atom with a double bond has two lone pairs, and the two oxygen atoms with single bonds have three lone pairs.
Also, there is a negative (-1) charge on the two oxygen atoms with single bonds, and a positive (+1) charge on the phosphorus atom.
Alternative method: Lewis structure of PO3–
Rough sketch
- First, determine the total number of valence electrons
In the periodic table, phosphorus lies in group 15, and oxygen lies in group 16.
Hence, phosphorus has five valence electrons and oxygen has six valence electrons.
Since PO3– has one phosphorus atom and three oxygen atoms, so…
Valence electrons of one phosphorus atom = 5 × 1 = 5
Valence electrons of three oxygen atoms = 6 × 3 = 18
Now the PO3– has a negative (-1) charge, so we have to add one more electron.
So the total valence electrons = 5 + 18 + 1 = 24
Learn how to find: Phosphorus valence electrons and Oxygen valence electrons
- Second, find the total electron pairs
We have a total of 24 valence electrons. And when we divide this value by two, we get the value of total electron pairs.
Total electron pairs = total valence electrons ÷ 2
So the total electron pairs = 24 ÷ 2 = 12
- Third, determine the central atom
We have to place the least electronegative atom at the center.
Since phosphorus is less electronegative than oxygen, assume that the central atom is phosphorus.
Therefore, place phosphorus in the center and oxygens on either side.
- And finally, draw the rough sketch
Lone pair
Here, we have a total of 12 electron pairs. And three P — O bonds are already marked. So we have to only mark the remaining nine electron pairs as lone pairs on the sketch.
Also remember that phosphorus is a period 3 element, so it can keep more than 8 electrons in its last shell. And oxygen is a period 2 element, so it can not keep more than 8 electrons in its last shell.
Always start to mark the lone pairs from outside atoms. Here, the outside atoms are oxygens.
So for each oxygen, there are three lone pairs, and for phosphorus, there is zero lone pair because all nine electron pairs are over.
Mark the lone pairs on the sketch as follows:
Formal charge
Use the following formula to calculate the formal charges on atoms:
Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons
For phosphorus atom, formal charge = 5 – 0 – ½ (6) = +2
For each oxygen atom, formal charge = 6 – 6 – ½ (2) = -1
Here, both phosphorus and oxygen atoms have charges, so mark them on the sketch as follows:
The above structure is not a stable Lewis structure because both phosphorus and oxygen atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.
Convert a lone pair of the oxygen atom to make a new P — O bond with the phosphorus atom as follows:
Final structure
The final structure of PO3– consists of a central phosphorus atom linked to one oxygen atom through a double covalent bond and to the remaining two oxygen atoms via single covalent bonds. In this arrangement, the phosphorus atom satisfies the octet rule by forming four covalent bonds with the surrounding oxygen atoms, leaving it with no lone pairs. Each of the two single-bonded oxygen atoms completes its octet with three lone pairs, while the double-bonded oxygen atom retains two. This specific configuration is preferred because it results in a formal charge of +1 on the phosphorus atom and -1 on each of the single-bonded oxygens, which accurately represents the electron distribution for this anion. Consequently, this electronic pattern serves as the definitive and most accurate Lewis representation for this ion.
To complete the representation, draw square brackets around the entire Lewis structure and place a “-” or “-1” sign as a superscript outside the upper right bracket. This notation signifies that the negative charge is a property of the whole ion.
FAQs
How many valence electrons are in PO3– ion?
We can calculate the total number of valence electrons for PO3– by adding up the valence electrons of each atom in the ion.
Phosphorus, which is in group 5 of the periodic table, has five valence electrons. And each oxygen atom has six valence electrons. Also, PO3– has a negative (-1) charge, so we have to add one more electron.
Therefore, the PO3– ion has a total of 5 + 6(3) + 1 = 24 valence electrons.
What’s the formal charge on each atom in PO3– ion?
The PO3– ion has one phosphorus atom and three oxygen atoms. The central atom (phosphorus) has a formal charge of +1. One oxygen atom with a double bond has a formal charge of 0, and the remaining two oxygen atoms with single bonds have -1 formal charge.
Does PO3– satisfy the octet rule for all atoms?
The most stable Lewis structure of PO3– ion contains phosphorus, the central atom that makes one double bond and two single bonds with the surrounding three oxygen atoms, forming an octet. And each oxygen atom also has eight electrons in its outer shell resulting in a full octet.
Therefore, the PO3– satisfies the octet rule for all atoms.
Next: CH3CHO Lewis structure
External links
- https://www.quora.com/How-can-you-determine-the-Lewis-structure-of-PO3
- https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/PO3-3minus-lewis-structure.html
- https://www.numerade.com/ask/question/draw-the-lewis-structure-of-po3-76028/
- https://www.chegg.com/homework-help/questions-and-answers/21-po3-phosphate-ion-draw-lewis-structure-counting-valence-clectrons-atom–determine-elect-q26034565
Deep
Learnool.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.