AsCl5 Lewis structure

AsCl₅ (arsenic pentachloride) has one arsenic atom and five chlorine atoms.

In AsCl₅ Lewis structure, there are five single bonds around the arsenic atom, with five chlorine atoms attached to it, and on each chlorine atom, there are three lone pairs.

Alternative method: Lewis structure of AsCl₅

Rough sketch

• First, determine the total number of valence electrons

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

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

Since AsCl₅ has one arsenic atom and five chlorine atoms, so…

Valence electrons of one arsenic atom = 5 × 1 = 5
Valence electrons of five chlorine atoms = 7 × 5 = 35

And the total valence electrons = 5 + 35 = 40

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

• Second, find the total electron pairs

We have a total of 40 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 = 40 ÷ 2 = 20

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 20 electron pairs. And five As — Cl bonds are already marked. So we have to only mark the remaining fifteen 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 chlorine is a period 3 element, so it can keep more than 8 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are chlorines.

So for each chlorine, there are three lone pairs, and for arsenic, there is zero lone pair because all fifteen 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 (10) = 0

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

Here, both arsenic and chlorine atoms do not have charges, so no need to mark the charges.

Final structure

The final structure of AsCl₅ involves a central arsenic atom connected to five chlorine atoms through single covalent bonds. In this arrangement, the arsenic atom utilizes an expanded octet to form five bonding pairs, while each chlorine atom fulfills its octet by maintaining three lone pairs of its own. This configuration is the most stable because it results in formal charges of zero for all atoms involved, representing the most energetically favorable state for the molecule. As a result, this specific electronic distribution serves as the definitive and most accurate Lewis representation of arsenic pentachloride.

Next: COBr₂ Lewis structure

External links

• https://lambdageeks.com/ascl5-lewis-structure/
• https://study.com/academy/answer/what-is-the-lewis-dot-structure-for-ascl-5.html
• https://quizlet.com/explanations/questions/what-is-the-lewis-structure-of-the-compound-ascl_5-21c5adcc-321bae61-d642-48fc-9a12-a1fd9a2416e7?src=set_page_ssr
• https://www.answers.com/Q/What_is_the_Lewis_dot_structure_of_AsCl5