KrF4 Lewis structure

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KrF₄ (krypton tetrafluoride) has one krypton atom and four fluorine atoms.

In the KrF₄ Lewis structure, there are four single bonds around the krypton atom, with four fluorine atoms attached to it. Each fluorine atom has three lone pairs, and the krypton atom has two lone pairs.

Steps

Use these steps to correctly draw the KrF₄ Lewis structure:

#1 First draw a rough sketch
#2 Mark lone pairs on the atoms
#3 Calculate and mark formal charges on the atoms, if required

Let’s discuss each step in more detail.

#1 First draw a rough sketch

• First, determine the total number of valence electrons

In the periodic table, krypton lies in group 18, and fluorine lies in group 17.

Hence, krypton has eight valence electrons and fluorine has seven valence electrons.

Since KrF₄ has one krypton atom and four fluorine atoms, so…

Valence electrons of one krypton atom = 8 × 1 = 8
Valence electrons of four fluorine atoms = 7 × 4 = 28

And the total valence electrons = 8 + 28 = 36

Learn how to find: Krypton 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 krypton is less electronegative than fluorine, assume that the central atom is krypton.

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

• And finally, draw the rough sketch

#2 Mark lone pairs on the atoms

Here, we have a total of 18 electron pairs. And four Kr — 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 krypton 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 krypton, there are two lone pairs.

Mark the lone pairs on the sketch as follows:

#3 Calculate and mark formal charges on the atoms, if required

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

For krypton atom, formal charge = 8 – 4 – ½ (8) = 0

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

Here, both krypton and fluorine atoms do not have charges, so no need to mark the charges.

In the above structure, you can see that the central atom (krypton) forms an octet. And the outside atoms (fluorines) also form an octet. Hence, the octet rule is satisfied.

Therefore, this structure is the stable Lewis structure of KrF₄.

Next: BrO₄^– Lewis structure

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