Lewis structure of SnCl2

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Lewis structure of SnCl2
Lewis structure of SnCl2

The Lewis structure of SnCl2 contains two single bonds, with tin in the center, and two chlorines on either side. There are three lone pairs on each chlorine atom, and one lone pair on the tin atom.

Steps

By using the following steps, you can easily draw the Lewis structure of SnCl2.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Calculate formal charge and check stability (if octet is already completed on central atom)

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

  • Let’s calculate the total number of valence electrons

We know that… tin is a group 14 element and chlorine is a group 17 element. Hence, tin has four valence electrons and chlorine has seven valence electrons.

Now SnCl2 has one tin atom and two chlorine atoms.

So the total number of valence electrons = valence electrons of tin atom + (valence electrons of chlorine atom × 2)

Therefore, the total number of valence electrons = 4 + 14 = 16

  • Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for tin and chlorine as follows:

Electronegativity value of tin = 1.96
Electronegativity value of chlorine = 3.16

Obviously, tin is less electronegative than chlorine. Hence, assume that tin is the central atom.

So now, put tin in the center and chlorines on either side. And draw the rough skeleton structure for the Lewis structure of SnCl2 something like this:

Skeleton structure for Lewis structure of SnCl2

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since tin is surrounded by two chlorines, use four electrons to show two chemical bonds as follows:

Two chemical bonds shown between atoms

#3 Mark lone pairs

As calculated earlier, we have a total of 16 valence electrons. And in the above structure, we have already used four valence electrons. Hence, twelve valence electrons are remaining.

Two valence electrons represent one lone pair. So twelve valence electrons = six lone pairs.

Note that tin is a period 5 element, so it can keep more than 8 electrons in its last shell. And chlorine is a period 3 element, so it can keep more than 8 electrons in its last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are chlorines, so each chlorine will get three lone pairs. And the central atom (tin) will not get any lone pair, because all six lone pairs are used.

So the Lewis structure of SnCl2 looks something like this:

Lone pairs marked on Lewis structure of SnCl2

In the above structure, you can see that the octet is completed on the central atom (tin), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

#4 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

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

Collect the data from the above structure and then, write it down below as follows:

  • For tin atom

Valence electrons = 4
Nonbonding electrons = 2
Bonding electrons = 4

Formal charge = 4 – 2 – ½ (4) = 0

  • For each chlorine atom

Valence electrons = 7
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 7 – 6 – ½ (2) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of SnCl2 looks something like this:

Formal charges are calculated, and got the stable Lewis structure of SnCl2

In the above structure, you can see that the formal charges of both (tin and chlorine) are zero. Therefore, this is the stable Lewis structure of SnCl2.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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External links

Deep

Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.

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