SF4 (sulfur tetrafluoride) has one sulfur atom and four fluorine atoms. In the lewis structure of SF4, there are four single bonds around the sulfur atom, with four fluorine atoms attached to it. Each fluorine atom has three lone pairs, and the sulfur atom has one lone pair.
Here’s how you can draw the SF4 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
Hence, sulfur has six valence electrons and fluorine has seven valence electrons.
Since SF4 has one sulfur atom and four fluorine atoms, so…
Valence electrons of one sulfur atom = 6 × 1 = 6
Valence electrons of four fluorine atoms = 7 × 4 = 28
And the total valence electrons = 6 + 28 = 34
- Second, find the total electron pairs
We have a total of 34 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 = 34 ÷ 2 = 17
- 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
#2 Mark Lone Pairs
Here, we have a total of 17 electron pairs. And four S — F bonds are already marked. So we have to only mark the remaining thirteen electron pairs as lone pairs on the sketch.
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:
#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 (8) = 0
For each fluorine atom, formal charge = 7 – 6 – ½ (2) = 0
Here, both sulfur and fluorine atoms do not have charges, so no need to mark the charges.
And in the above structure, you can see that the central atom (sulfur) forms an octet. Hence, the octet rule is satisfied.
Therefore, this structure is the stable lewis structure of SF4.
Next: H2S Lewis Structure