# What is the Charge on PO4 (Phosphate ion)? And Why?

The Charge of PO4 (Phosphate ion) is 3-.

But the question is how can you find the charge on PO4 (phosphate ion)?

Well there are 2 methods by which you can find the charge of PO4.

Lets dive right into these methods one by one.

If you are a visual learner like me, then here is a short one minute video for you.

## Method 1: By looking at what it is bonded to

The charge of PO4 (Phosphate ion) can be found out by looking at what it is bonded to.

So let’s take some examples of compounds that contain PO4; like H3PO4, K3PO4, etc.

Example 1: H3PO4
In H3PO4, the PO4 is bonded to Hydrogen (H).
You know that the ionic charge of H is 1+.
So you can easily say that the charge of PO4 should be 3-, then only it will get canceled out.
Hence the charge of PO4 in H3PO4 is 3-.

Example 2: K3PO4
In K3PO4, the PO4 is bonded to Potassium (K).
And again, you know that the ionic charge of K is 1+.
So here also you can easily say that the charge of PO4 should be 3-, then only it will get canceled out.
Hence the charge of PO4 in K3PO4 is 3-.

As seen from the above examples,
The charge of PO4 is 3-.

In this way, you can easily find the charge of PO4 by looking at what it is bonded to.

## Method 2: By calculating the formal charge using lewis structure

In order to calculate the formal charge on PO4 (Phosphate ion), you should know the Lewis dot structure of PO4 (Phosphate ion).

Here is the lewis structure of PO4.

Now using the above lewis structure of PO4, you have to find the formal charge on each atom that is present in the PO4 molecule.

For calculating the formal charge, you need to remember this formula;

Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2

You can see the bonding and nonbonding electrons of PO4 from the image given below.

So now let’s calculate the formal charge on each individual atom present in PO4.

Formal charge on Phosphorus atom:
Valence electrons = 5 (as it is in group 15 on periodic table) [1]
Nonbonding electrons = 0
Bonding electrons = 10

So according to the formula of formal charge, you will get;

Formal charge on Phosphorus = Valence electrons – Nonbonding electrons – (Bonding electrons)/2 = 5 – 0 – (10/2) = 0

So the formal charge on phosphorus atom is 0.

Formal charge on double bonded Oxygen:
Valence electron = 6 (as it is in group 16 on periodic table) [2]
Nonbonding electrons = 4
Bonding electrons = 4

So according to the formula of formal charge, you will get;

Formal charge on double bonded Oxygen = Valence electrons – Nonbonding electrons – (Bonding electrons)/2 = 6 – 4 – (4/2) = 0

So the formal charge on double bonded oxygen atom is 0.

Formal charge on single bonded Oxygen:
Valence electron = 6 (as it is in group 16 on periodic table)
Nonbonding electrons = 6
Bonding electrons = 2

So according to the formula of formal charge, you will get;

Formal charge on single bonded Oxygen = Valence electrons – Nonbonding electrons – (Bonding electrons)/2 = 6 – 6 – (2/2) = 1-

So the formal charge on single bonded oxygen atom is 1-.

Now let’s put all these charges on the lewis dot structure of PO4.

So there is overall 3- charge left on the entire molecule.

This indicates that the PO4 (Phosphate ion) has 3- charge.

I hope you have understood the above calculations of PO4 (Phosphate ion). But for your tests, you don’t need to remember the entire calculations. You should just try to remember that PO4 has 3- charge.

Check out some other related topics for your practice.

Author
##### Jay Rana

Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. With a desire to make learning accessible for everyone, he founded Knords Learning, an online learning platform that provides students with easily understandable explanations.

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