Lewis Structure of SF3+

Lewis Structure of SF3+

SF3+ (sulfur trifluoride) has one sulfur atom and three fluorine atoms. In the lewis structure of SF3+, there are three single bonds around the sulfur atom, with three fluorine atoms attached to it. Each fluorine atom has three lone pairs, and the sulfur atom has one lone pair.

Also, there is a positive (+1) charge on the sulfur atom.


Here’s how you can draw the lewis structure of SF3+ 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, sulfur lies in group 16, and fluorine lies in group 17.

Hence, sulfur has six valence electrons and fluorine has seven valence electrons.

Since SF3+ has one sulfur atom and three fluorine atoms, so…

Valence electrons of one sulfur atom = 6 × 1 = 6
Valence electrons of three fluorine atoms = 7 × 3 = 21

Now the SF3+ has a positive (+1) charge, so we have to subtract one electron.

So the total valence electrons = 6 + 21 – 1 = 26

  • Second, find the total electron pairs

We have a total of 26 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 = 26 ÷ 2 = 13

  • Third, determine the central atom

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

Since sulfur is less electronegative than fluorine, assume that the central atom is sulfur.

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

  • And finally, draw the rough sketch
Lewis Structure of SF3+ (Step 1)

#2 Mark Lone Pairs

Here, we have a total of 13 electron pairs. And three S — F bonds are already marked. So we have to only mark the remaining ten electron pairs as lone pairs on the sketch.

Also remember that sulfur 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 sulfur, there is one lone pair.

Mark the lone pairs on the sketch as follows:

Lewis Structure of SF3+ (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 sulfur atom, formal charge = 6 – 2 – ½ (6) = +1

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

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

Lewis Structure of SF3+ (Step 3)

In the above structure, you can see that the central atom (sulfur) forms an octet. Hence, the octet rule is satisfied.

Now there is still a positive (+1) charge on the sulfur atom.

This is okay, because the structure with a positive charge on the least electronegative atom is the best lewis structure. And in this case, the least electronegative element is sulfur.

Therefore, this structure is the most stable lewis structure of SF3+.

And since the SF3+ has a positive (+1) charge, mention that charge on the lewis structure by drawing brackets as follows:

Lewis Structure of SF3+ (Final)

Next: HOCN Lewis Structure

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