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KrF2 (krypton difluoride) has one krypton atom and two fluorine atoms.
In the KrF2 Lewis structure, there are two single bonds around the krypton atom, with two fluorine atoms attached to it, and each atom has three lone pairs.
Steps
Use these steps to correctly draw the KrF2 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 KrF2 has one krypton atom and two fluorine atoms, so…
Valence electrons of one krypton atom = 8 × 1 = 8
Valence electrons of two fluorine atoms = 7 × 2 = 14
And the total valence electrons = 8 + 14 = 22
Learn how to find: Krypton valence electrons and Fluorine valence electrons
- Second, find the total electron pairs
We have a total of 22 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 = 22 ÷ 2 = 11
- 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 11 electron pairs. And two Kr — F bonds are already marked. So we have to only mark the remaining nine 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 atom, there are three 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 – 6 – ½ (4) = 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 KrF2.
Next: BeCl2 Lewis structure
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Deep
Learnool.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.