What is the Charge on Bromate ion (BrO3)? And Why?

The Charge of BrO3 (Bromate ion) is 1-.

But the question is how can you find the charge on BrO3 (bromate ion)?

Well there are 2 methods by which you can find the charge of BrO3.

Lets dive right into these methods one by one.

You can also refer to the below video from which you will learn to find charge of any ion.

Method 1: By looking at what it is bonded to

The charge of BrO3 (Bromate ion) can be found out by looking at what it is bonded to.

So let’s take some examples of compounds that contain BrO₃; like NaBrO₃, KBrO₃, etc.

Example 1: NaBrO₃
In NaBrO₃, the BrO₃ is bonded to Sodium (Na).
You know that the ionic charge of Na is 1+.
So you can easily say that the charge of BrO₃ should be 1-, then only it will get canceled out.
Hence the charge of BrO₃ in NaBrO₃ is 1-.

Example 2: KBrO₃
In KBrO₃, the BrO₃ 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 BrO₃ should be 1-, then only it will get canceled out.
Hence the charge of BrO₃ in KBrO₃ is 1-.

As seen from the above examples,
The charge of BrO3 is 1-.

In this way, you can easily find the charge of BrO3 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 BrO3 (Bromate ion), you should know the Lewis dot structure of BrO3 (Bromate ion).

Here is the lewis structure of BrO3.

Now using the above lewis structure of BrO3, you have to find the formal charge on each atom that is present in the BrO3 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 BrO3 from the image given below.

So now let’s calculate the formal charge on each individual atom present in BrO3.

Formal charge on Bromine atom:
Valence electrons = 7 (as it is in group 17 on periodic table) ^[1]
Nonbonding electrons = 2
Bonding electrons = 10

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

Formal charge on Bromine = Valence electrons – Nonbonding electrons – (Bonding electrons)/2 = 7 – 2 – (10/2) = 0

So the formal charge on bromine atom is 0.

Formal charge on double bonded Oxygen atom:
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 atom:
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 BrO3.

So there is overall 1- charge left on the entire molecule.

This indicates that the BrO3 (Bromate ion) has 1- charge.

I hope you have understood the above calculations of BrO3 (Bromate ion). But for your tests, you don’t need to remember the entire calculations. You should just try to remember that BrO3 has 1- charge.

Check out some other related topics for your practice.

Related topics:
Charge on SCN
Charge on H3PO4
Charge on HSO4 (Hydrogen Sulfate ion)
Charge on Methane (CH4)
Charge of Antimony (Sb)