BrF4- Lewis structure

BrF₄^– has one bromine atom and four fluorine atoms.

In BrF₄^– Lewis structure, there are four single bonds around the bromine atom, with four fluorine atoms attached to it, and on each fluorine atom, there are three lone pairs.

Also, there is a negative (-1) charge on the bromine atom.

Alternative method: Lewis structure of BrF₄^–

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, both bromine and fluorine lie in group 17.

Hence, both bromine and fluorine have seven valence electrons.

Since BrF₄^– has one bromine atom and four fluorine atoms, so…

Valence electrons of one bromine atom = 7 × 1 = 7
Valence electrons of four fluorine atoms = 7 × 4 = 28

Now the BrF₄^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 7 + 28 + 1 = 36

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

• Second, find the total electron pairs

We have a total of 36 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 = 36 ÷ 2 = 18

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 18 electron pairs. And four Br — F bonds are already marked. So we have to only mark the remaining fourteen 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 fluorine 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 fluorines.

So for each fluorine, there are three lone pairs, and for bromine, there are two lone pairs.

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 – 4 – ½ (8) = -1

For each fluorine atom, formal charge = 7 – 6 – ½ (2) = 0

Here, the bromine atom has a charge, so mark it on the sketch as follows:

Final structure

The final structure of BrF₄^– contains a central bromine atom connected to four fluorine atoms through single covalent bonds. In this layout, the bromine atom utilizes an expanded valence shell to accommodate twelve electrons, consisting of four bonding pairs and two lone pairs. Each fluorine atom fulfills the octet rule by maintaining three lone pairs alongside its single shared bond. This arrangement represents the most stable state for the ion because it results in a formal charge of -1 for the central bromine atom, while all four fluorine atoms carry a formal charge of zero. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of the BrF₄^– 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.

Next: AsF₆^– Lewis structure

External video

• How to Draw the Lewis Dot Structure for BrF4- – YouTube • Wayne Breslyn

External links

• https://lambdageeks.com/brf4-lewis-structure/
• https://www.numerade.com/ask/question/draw-lewis-structure-for-brf4-b-what-is-the-electron-pair-geometry-for-br-in-brf4-c-what-is-the-the-shape-molecular-geometry-of-brf4-69896/
• https://www.chegg.com/homework-help/questions-and-answers/draw-lewis-structure-brf4-b-electron-pair-geometry-br-brf4-c-shape-molecular-geometry-brf4-q39219394
• https://homework.study.com/explanation/give-the-lewis-structure-of-brf4-and-determine-the-number-of-valence-electrons.html
• https://quizlet.com/explanations/questions/draw-the-lewis-structure-for-cebrf4-a2e83524-62a52e93-5f19-474e-b30b-8cba0ec91e6f