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.

Alternative method: Lewis structure of AsF₄^–

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 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

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

• 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

Lone pair

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:

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 – 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:

Final structure

The final structure of AsF₄^– has a central arsenic atom connected to four fluorine atoms through single covalent bonds. Within this layout, the arsenic atom serves as an exception to the octet rule, utilizing an expanded valence shell to accommodate ten electrons, which include four bonding pairs and one lone pair. Each fluorine atom fulfills its octet by maintaining three lone pairs of its own alongside the single shared bond. This arrangement is the most stable because it optimizes the formal charge distribution; the arsenic atom carries a formal charge of -1, while all four fluorine atoms maintain a formal charge of zero. Accordingly, this specific electronic distribution serves as the definitive and most accurate Lewis representation of AsF₄^–.

To complete the representation, draw square brackets around the entire Lewis structure and place a “-” or “-1” sign as a superscript outside the upper right bracket. This notation signifies that the negative charge is a property of the whole ion.

Next: NS₂ Lewis structure

External links

• https://www.chegg.com/homework-help/questions-and-answers/asf4-obey-octet-rule-draw-lewis-structure-including-lone-pair-electrons-nonzero-formal-cha-q7739959
• https://www.numerade.com/ask/question/draw-the-lewis-structure-of-asf4-use-this-stnicture-conjunction-with-vsepr-theory-predict-the-electron-domain-geometry-of-the-molecule-the-molecular-geometry-shape-ofthe-molecule-the-bond-an-54229/
• https://oneclass.com/homework-help/chemistry/7027453-asf4-lewis-structure.en.html