AsF6- Lewis structure

AsF₆^– has one arsenic atom and six fluorine atoms.

In AsF₆^– Lewis structure, there are six single bonds around the arsenic atom, with six fluorine atoms attached to it, and on each fluorine atom, there are three lone pairs.

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

Alternative method: Lewis structure of AsF₆^–

Rough sketch

• 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 AsF₆^– has one arsenic atom and six fluorine atoms, so…

Valence electrons of one arsenic atom = 5 × 1 = 5
Valence electrons of six fluorine atoms = 7 × 6 = 42

Now the AsF₆^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 5 + 42 + 1 = 48

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

• Second, find the total electron pairs

We have a total of 48 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 = 48 ÷ 2 = 24

• 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

Lone pair

Here, we have a total of 24 electron pairs. And six As — F bonds are already marked. So we have to only mark the remaining eighteen 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 zero lone pair because all eighteen electron pairs are over.

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 arsenic atom, formal charge = 5 – 0 – ½ (12) = -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:

Final structure

The final structure of AsF₆^– features a central arsenic atom connected to six fluorine atoms through single covalent bonds. Within this layout, the arsenic atom utilizes an expanded valence shell to accommodate twelve electrons, which are involved in the six bonding pairs. Each fluorine atom fulfills the octet rule by maintaining three lone pairs in addition to its single shared bond. This configuration represents the most stable electronic state for the ion because it results in a formal charge of -1 on the central arsenic atom, while all six fluorine atoms carry a formal charge of zero. Consequently, this specific electronic distribution serves as the definitive and most accurate Lewis representation of the AsF₆^– ion.

To properly represent this as a polyatomic ion, the entire Lewis structure is enclosed within square brackets. The overall charge of 1- is then written as a superscript outside the brackets at the top right, indicating that the structure possesses one additional electron beyond the valence count of the neutral atoms.

Next: CH₃O^– Lewis structure

External video

• AsF6- Lewis Structure: How to Draw the Lewis Structure for Arsenic Hexafluoride ion – YouTube • Wayne Breslyn

External links

• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/AsF6-Lewis-structure.html
• https://lambdageeks.com/asf6-lewis-structure/
• https://homework.study.com/explanation/draw-lewis-structure-for-a-co-b-asf6.html
• https://www.chegg.com/homework-help/questions-and-answers/lewis-structure-asf6-q1611779