PO2- Lewis structure

PO₂^– has one phosphorus atom and two oxygen atoms.

In PO₂^– Lewis structure, there is one double bond and one single bond around the phosphorus atom, with two oxygen atoms attached to it. The oxygen atom with a double bond has two lone pairs, the oxygen atom with a single bond has three lone pairs, and the phosphorus atom has one lone pair.

Also, there is a negative (-1) charge on the oxygen atom with a single bond.

Alternative method: Lewis structure of PO₂^–

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 PO₂^– has one phosphorus atom and two oxygen atoms, so…

Valence electrons of one phosphorus atom = 5 × 1 = 5
Valence electrons of two oxygen atoms = 6 × 2 = 12

Now the PO₂^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 5 + 12 + 1 = 18

Learn how to find: Phosphorus valence electrons and Oxygen valence electrons

• Second, find the total electron pairs

We have a total of 18 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 = 18 ÷ 2 = 9

• 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 9 electron pairs. And two P — O bonds are already marked. So we have to only mark the remaining seven 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 one lone pair.

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 – 2 – ½ (4) = +1

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 PO₂^– includes a central phosphorus atom linked to two oxygen atoms. In this configuration, the phosphorus atom forms a double covalent bond with one oxygen atom and a single covalent bond with the other, while retaining one lone pair. Within this layout, both oxygen atoms fulfill the octet rule: the double-bonded oxygen maintains two lone pairs, and the single-bonded oxygen maintains three lone pairs. The phosphorus atom also satisfies the octet rule with its three bonding pairs and one lone pair. This arrangement represents the most stable state for the ion because the negative formal charge is located on an oxygen atom, while the other atoms maintain a formal charge of zero. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of PO₂^–.

To properly represent this as a polyatomic ion, the entire Lewis structure is enclosed within square brackets. The overall charge of 1- is then written as a superscript outside the brackets at the top right, indicating that the structure possesses one additional electron beyond the valence count of the neutral atoms.

Next: C₂F₆ Lewis structure

External links

• https://www.numerade.com/ask/question/draw-the-lewis-structure-for-po2-and-then-answer-the-questions-below-to-describe-your-structure-1-determine-the-number-of-valence-electrons-2-what-is-the-central-atom-3-how-many-atoms-are-si-26804/
• https://www.chegg.com/homework-help/questions-and-answers/draw-lewis-structure-polyatomic-ion-po2-predict-molecular-geometry-include-resonance-struc-q70161749
• https://www.bartleby.com/questions-and-answers/please-draw-the-lewis-structure-of-the-polyatomic-ion-po2-without-forgetting-the-resonance-structure/6e035c2d-4210-4ea3-94d3-80973352dd70