SbCl52- has one antimony atom and five chlorine atoms. In the lewis structure of SbCl52-, there are five single bonds around the antimony atom, with five chlorine atoms attached to it. Each chlorine atom has three lone pairs, and the antimony atom has one lone pair.
Also, there is a negative (-2) charge on the antimony atom.
Here’s how you can draw the SbCl52- 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, antimony has five valence electrons and chlorine has seven valence electrons.
Since SbCl52- has one antimony atom and five chlorine atoms, so…
Valence electrons of one antimony atom = 5 × 1 = 5
Valence electrons of five chlorine atoms = 7 × 5 = 35
Now the SbCl52- has a negative (-2) charge, so we have to add two more electrons.
So the total valence electrons = 5 + 35 + 2 = 42
- Second, find the total electron pairs
We have a total of 42 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 = 42 ÷ 2 = 21
- Third, determine the central atom
We have to place the least electronegative atom at the center.
Since antimony is less electronegative than chlorine, assume that the central atom is antimony.
Therefore, place antimony in the center and chlorines on either side.
- And finally, draw the rough sketch
#2 Mark Lone Pairs
Here, we have a total of 21 electron pairs. And five Sb — Cl bonds are already marked. So we have to only mark the remaining sixteen electron pairs as lone pairs on the sketch.
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 antimony, 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 antimony atom, formal charge = 5 – 2 – ½ (10) = -2
For each chlorine atom, formal charge = 7 – 6 – ½ (2) = 0
Here, the antimony atom has a charge, so mark it on the sketch as follows:
In the above structure, you can see that the central atom (antimony) forms an octet. Hence, the octet rule is satisfied.
Now there is still a negative (-2) charge on the antimony atom.
This is not okay, right? Because the structure with a negative charge on the most electronegative atom is the best lewis structure. And in this case, the most electronegative element is chlorine.
But if we convert a lone pair of the antimony atom to make a new Sb — Cl bond with the chlorine atom, and calculate the formal charge, then we do not get the formal charges on atoms closer to zero.
And the structure with the formal charges on atoms closer to zero is the best lewis structure.
Therefore, this structure is the most stable lewis structure of SbCl52-.
And since the SbCl52- has a negative (-2) charge, mention that charge on the lewis structure by drawing brackets as follows:
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