GaCl3 Lewis structure

GaCl₃ (gallium trichloride) has one gallium atom and three chlorine atoms.

In GaCl₃ Lewis structure, there are three single bonds around the gallium atom, with three chlorine atoms attached to it, and on each chlorine atom, there are three lone pairs.

Alternative method: Lewis structure of GaCl₃

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, gallium lies in group 13, and chlorine lies in group 17.

Hence, gallium has three valence electrons and chlorine has seven valence electrons.

Since GaCl₃ has one gallium atom and three chlorine atoms, so…

Valence electrons of one gallium atom = 3 × 1 = 3
Valence electrons of three chlorine atoms = 7 × 3 = 21

And the total valence electrons = 3 + 21 = 24

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

• Second, find the total electron pairs

We have a total of 24 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 = 24 ÷ 2 = 12

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 12 electron pairs. And three Ga — Cl bonds are already marked. So we have to only mark the remaining nine electron pairs as lone pairs on the sketch.

Also remember that gallium 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 gallium, there is zero lone pair because all nine 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 gallium atom, formal charge = 3 – 0 – ½ (6) = 0

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

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

Final structure

The final structure of GaCl₃ involves a central gallium atom connected to three chlorine atoms through single covalent bonds. In this arrangement, the gallium atom serves as an exception to the octet rule, possessing an incomplete valence shell with only six electrons across three bonding pairs. Each chlorine atom fulfills its octet by maintaining three lone pairs of its own alongside the single shared bond. 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. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of gallium(III) chloride.

Next: NSF Lewis structure

External video

• How to Draw the Lewis Dot Structure for GaCl3: Gallium trichloride – YouTube • Wayne Breslyn

External links

• https://lambdageeks.com/gacl3-lewis-structure/
• https://www.chegg.com/homework-help/questions-and-answers/3-draw-lewis-structure-ionic-compound-kf-b-li3n-c-gacl3-q36108786