PCl2- Lewis structure

PCl₂^– has one phosphorus atom and two chlorine atoms.

In PCl₂^– Lewis structure, there are two single bonds around the phosphorus atom, with two chlorine atoms attached to it. Each chlorine atom has three lone pairs, and the phosphorus atom has two lone pairs.

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

Alternative method: Lewis structure of PCl₂^–

Rough sketch

• First, determine the total number of valence electrons

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

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

Since PCl₂^– has one phosphorus atom and two chlorine atoms, so…

Valence electrons of one phosphorus atom = 5 × 1 = 5
Valence electrons of two chlorine atoms = 7 × 2 = 14

Now the PCl₂^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 5 + 14 + 1 = 20

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

• Second, find the total electron pairs

We have a total of 20 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 = 20 ÷ 2 = 10

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 10 electron pairs. And two P — Cl bonds are already marked. So we have to only mark the remaining eight electron pairs as lone pairs on the sketch.

Also remember that both (phosphorus and chlorine) are the period 3 elements, so they can keep more than 8 electrons in their 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 phosphorus, there are two lone pairs.

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 phosphorus atom, formal charge = 5 – 4 – ½ (4) = -1

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

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

Final structure

The final structure of PCl₂^– consists of a central phosphorus atom linked to two chlorine atoms through single covalent bonds. In this arrangement, the phosphorus atom satisfies the octet rule by forming two bonding pairs and retaining two lone pairs. Within this layout, each chlorine atom successfully reaches a stable octet by maintaining three lone pairs alongside its single shared bond. This configuration represents the most stable state for the ion because it results in a formal charge of -1 on the central phosphorus atom, while each chlorine atom maintains a formal charge of zero. Accordingly, this specific electronic distribution serves as the definitive and most accurate Lewis representation of PCl₂^–.

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: AsO₂^– Lewis structure

External video

• PCl2- Lewis Structure: How to Draw the Lewis Structure for PCl2- – YouTube • Wayne Breslyn

External links

• https://www.chegg.com/homework-help/questions-and-answers/lewis-dot-structure-pcl2-q26095774