AlF3 Lewis Structure

AlF3 Lewis Structure

AlF3 (aluminum fluoride) has one aluminum atom and three fluorine atoms. In the lewis structure of AlF3, there are three single bonds around the aluminum atom, with three fluorine atoms attached to it, and on each fluorine atom, there are three lone pairs.

Steps

Here’s how you can draw the AlF3 lewis structure step by step.

Step #1: draw sketch
Step #2: mark lone pairs
Step #3: mark charges (if there are)

Let’s break down each step in detail.

#1 Draw Sketch

  • First, determine the total number of valence electrons

In the periodic table, aluminum lies in group 13, and fluorine lies in group 17.

Hence, aluminum has three valence electrons and fluorine has seven valence electrons.

Since AlF3 has one aluminum atom and three fluorine atoms, so…

Valence electrons of one aluminum atom = 3 × 1 = 3
Valence electrons of three fluorine atoms = 7 × 3 = 21

And the total valence electrons = 3 + 21 = 24

  • 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 aluminum is less electronegative than fluorine, assume that the central atom is aluminum.

Therefore, place aluminum in the center and fluorines on either side.

  • And finally, draw the rough sketch
AlF3 Lewis Structure (Step 1)

#2 Mark Lone Pairs

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

Also remember that aluminum is a period 3 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 aluminum, there is zero lone pair because all nine electron pairs are over.

Mark the lone pairs on the sketch as follows:

AlF3 Lewis Structure (Step 2)

#3 Mark Charges

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

For aluminum atom, formal charge = 3 – 0 – ½ (6) = 0

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

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

In the above structure, you can see that the central atom (aluminum) doesn’t form an octet. But, aluminum has an exception that it does not require eight electrons to form an octet. So no need to worry about the octet rule here.

Therefore, this structure is the stable lewis structure of AlF3.

Next: TeF4 Lewis Structure

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