BrO3- Lewis structure

BrO₃^– (bromate) has one bromine atom and three oxygen atoms.

In the BrO₃^– Lewis structure, there is one single bond and two double bonds around the bromine atom, with three oxygen atoms attached to it. The oxygen atom with a single bond has three lone pairs, the two oxygen atoms with double bonds have two lone pairs, and the bromine 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 BrO₃^–

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, bromine lies in group 17, and oxygen lies in group 16.

Hence, bromine has seven valence electrons and oxygen has six valence electrons.

Since BrO₃^– has one bromine atom and three oxygen atoms, so…

Valence electrons of one bromine atom = 7 × 1 = 7
Valence electrons of three oxygen atoms = 6 × 3 = 18

Now the BrO₃^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 7 + 18 + 1 = 26

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

• Second, find the total electron pairs

We have a total of 26 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 = 26 ÷ 2 = 13

• Third, determine the central atom

We have to place the least electronegative atom at the center.

Since bromine is less electronegative than oxygen, assume that the central atom is bromine.

Therefore, place bromine in the center and oxygens on either side.

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 13 electron pairs. And three Br — O bonds are already marked. So we have to only mark the remaining ten electron pairs as lone pairs on the sketch.

Also remember that bromine is a period 4 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 bromine, 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 bromine atom, formal charge = 7 – 2 – ½ (6) = +2

For each oxygen atom, formal charge = 6 – 6 – ½ (2) = -1

Here, both bromine and oxygen atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both bromine 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 Br — O bond with the bromine atom as follows:

Since there are charges on bromine and oxygen atoms, again convert a lone pair of the oxygen atom to make a new Br — O bond with the bromine atom as follows:

Final structure

The final structure of BrO₃^– comprises a central bromine atom connected to three oxygen atoms. In this configuration, the bromine atom forms two double bonds with two of the oxygen atoms and a single covalent bond with the third oxygen atom, utilizing an expanded valence shell to accommodate twelve electrons (including one lone pair). Within this layout, the two double-bonded oxygen atoms each maintain two lone pairs, while the single-bonded oxygen atom fulfills its octet by retaining three lone pairs. This arrangement represents the most stable state for the ion because it minimizes formal charges, leaving a -1 charge on the single-bonded oxygen and a formal charge of zero on the bromine and the remaining oxygens. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of the bromate ion.

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: CBr₄ Lewis structure

External video

• BrO3- Lewis Structure: How to Draw the Lewis Structure for BrO3- – YouTube • Wayne Breslyn

External links

• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/BrO3–lewis-structure.html
• https://lambdageeks.com/bro3-lewis-structure/
• https://topblogtenz.com/bro3-lewis-structure-molecular-geometry-polarity/
• https://www.chemistryscl.com/general/BrO3–lewis-structure/
• https://socratic.org/questions/does-the-lewis-structure-for-bro-3-have-three-double-bonds-or-two-double-bonds