# AsF4- Lewis structure

AsF4 has one arsenic atom and four fluorine atoms.

In AsF4 Lewis structure, there are four single bonds around the arsenic atom, with four fluorine atoms attached to it. Each fluorine atom has three lone pairs, and the arsenic atom has one lone pair.

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

Contents

## Steps

To properly draw the AsF4 Lewis structure, follow these steps:

#1 Draw a rough sketch of the structure
#2 Next, indicate lone pairs on the atoms
#3 Indicate formal charges on the atoms, if necessary

Let’s break down each step in more detail.

### #1 Draw a rough sketch of the structure

• First, determine the total number of valence electrons

In the periodic table, arsenic lies in group 15, and fluorine lies in group 17.

Hence, arsenic has five valence electrons and fluorine has seven valence electrons.

Since AsF4 has one arsenic atom and four fluorine atoms, so…

Valence electrons of one arsenic atom = 5 × 1 = 5
Valence electrons of four fluorine atoms = 7 × 4 = 28

Now the AsF4 has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 5 + 28 + 1 = 34

• Second, find the total electron pairs

We have a total of 34 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 = 34 ÷ 2 = 17

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

### #2 Next, indicate lone pairs on the atoms

Here, we have a total of 17 electron pairs. And four As — F bonds are already marked. So we have to only mark the remaining thirteen electron pairs as lone pairs on the sketch.

Also remember that arsenic 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 arsenic, there is one lone pair.

Mark the lone pairs on the sketch as follows:

### #3 Indicate formal charges on the atoms, if necessary

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

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

For arsenic atom, formal charge = 5 – 2 – ½ (8) = -1

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

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

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

Therefore, this structure is the most stable Lewis structure of AsF4.

And since the AsF4 has a negative (-1) charge, mention that charge on the Lewis structure by drawing brackets as follows:

Next: NS2 Lewis structure