SnCl2 [tin(Ⅱ) chloride] has one tin atom and two chlorine atoms. In the lewis structure of SnCl2, there are two single bonds around the tin atom, with two chlorine atoms attached to it. Each chlorine atom has three lone pairs, and the tin atom has one lone pair.
Here’s how you can draw the SnCl2 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, tin has four valence electrons and chlorine has seven valence electrons.
Since SnCl2 has one tin atom and two chlorine atoms, so…
Valence electrons of one tin atom = 4 × 1 = 4
Valence electrons of two chlorine atoms = 7 × 2 = 14
And the total valence electrons = 4 + 14 = 18
- Second, find the total electron pairs
We have a total of 18 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 = 18 ÷ 2 = 9
- Third, determine the central atom
We have to place the least electronegative atom at the center.
Since tin is less electronegative than chlorine, assume that the central atom is tin.
Therefore, place tin in the center and chlorines on either side.
- And finally, draw the rough sketch
#2 Mark Lone Pairs
Here, we have a total of 9 electron pairs. And two Sn — Cl bonds are already marked. So we have to only mark the remaining seven 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 tin, 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 tin atom, formal charge = 4 – 2 – ½ (4) = 0
For each chlorine atom, formal charge = 7 – 6 – ½ (2) = 0
Here, both tin and chlorine atoms do not have charges, so no need to mark the charges.
In the above structure, you can see that the central atom (tin) doesn’t form an octet. But, tin 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 SnCl2.
Next: CH3COO– Lewis Structure