AsF6- Lewis Structure in 5 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

AsF6- lewis structure has an Arsenic atom (As) at the center which is surrounded by six Fluorine atoms (F). There are 6 single bonds between the Arsenic atom (As) and each Fluorine atom (F). There is a -1 formal charge on the Arsenic atom (As). 

If you haven’t understood anything from the above image of AsF6- lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of AsF6- ion.

So let’s move to the steps of drawing the lewis structure of AsF6- ion.

Steps of drawing AsF6- lewis structure

Step 1: Find the total valence electrons in AsF6- ion

In order to find the total valence electrons in an AsF6- ion, first of all you should know the valence electrons present in arsenic atom as well as fluorine atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of arsenic as well as fluorine using a periodic table.

Total valence electrons in AsF6- ion

→ Valence electrons given by arsenic atom:

Arsenic is a group 15 element on the periodic table. ^[1] Hence the valence electrons present in arsenic is 5.

You can see the 5 valence electrons present in the arsenic atom as shown in the above image.

→ Valence electrons given by fluorine atom:

Fluorine is group 17 element on the periodic table. ^[2] Hence the valence electron present in fluorine is 7.

You can see the 7 valence electrons present in the fluorine atom as shown in the above image.

Hence, 

Total valence electrons in AsF6- ion = valence electrons given by 1 arsenic atom + valence electrons given by 6 fluorine atoms + 1 more electron is added due to 1 negative charge = 5 + 7(6) + 1 = 48.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

Now here the given ion is AsF6- ion and it contains arsenic atom (As) and fluorine atoms (F).

You can see the electronegativity values of arsenic atom (As) and fluorine atom (F) in the above periodic table.

If we compare the electronegativity values of arsenic (As) and fluorine (F) then the arsenic atom is less electronegative.

So here the arsenic atom (As) is the center atom and the fluorine atoms (F) are the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the AsF6 molecule, you have to put the electron pairs between the arsenic atom (As) and fluorine atoms (F).

This indicates that the arsenic (As) and fluorine (F) are chemically bonded with each other in a AsF6 molecule.

Step 4: Make the outer atoms stable

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of AsF6 molecule, you can see that the outer atoms are fluorine atoms.

These outer fluorine atoms are forming an octet and hence they are stable.

Also, in step 1 we have calculated the total number of valence electrons present in the AsF6- ion.

The AsF6- ion has a total 48 valence electrons and all these valence electrons are used in the above sketch.

Hence there are no remaining electron pairs to be kept on the central atom. 

So now let’s proceed to the next step.

Step 5: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of AsF6.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on arsenic (As) atom as well as fluorine (F) atoms present in the AsF6 molecule.

For calculating the formal charge, you have to use the following formula;

Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons

You can see the number of bonding electrons and nonbonding electrons for each atom of AsF6 molecule in the image given below.

For Arsenic (As) atom:
Valence electrons = 5 (because arsenic is in group 15)
Bonding electrons = 12
Nonbonding electrons = 0

For Fluorine (F) atom:
Valence electrons = 7 (because fluorine is in group 17)
Bonding electrons = 2
Nonbonding electrons = 6

Formal charge	=	Valence electrons	–	(Bonding electrons)/2	–	Nonbonding electrons
As	=	5	–	12/2	–	0	=	0
F	=	7	–	2/2	–	6	=	0

From the above calculations of formal charge, you can see that the arsenic (As) atom has -1 charge and the fluorine (F) atoms has 0 charge.

So let’s keep these charges on the respective atoms in the AsF6 molecule.

This overall -1 charge on the AsF6 molecule is represented in the image given below.

In the above lewis dot structure of AsF6- ion, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of AsF6- ion.

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

SeCl2 Lewis Structure	C2F4 Lewis Structure
IBr3 Lewis Structure	HBrO Lewis Structure
IO2- Lewis Structure	CI4 Lewis Structure