SiH2Cl2 Lewis structure

SiH2Cl2 (dichlorosilane) has one silicon atom, two hydrogen atoms, and two chlorine atoms.

In SiH2Cl2 Lewis structure, there are four single bonds around the silicon atom, with two hydrogen atoms and two chlorine atoms attached to it, and on each chlorine atom, there are three lone pairs.

Contents

Steps

Here’s how you can easily draw the SiH2Cl2 Lewis structure step by step:

#1 Draw a rough skeleton structure
#2 Mention lone pairs on the atoms
#3 If needed, mention formal charges on the atoms

Now, let’s take a closer look at each step mentioned above.

#1 Draw a rough skeleton structure

• First, determine the total number of valence electrons

In the periodic table, silicon lies in group 14, hydrogen lies in group 1, and chlorine lies in group 17.

Hence, silicon has four valence electrons, hydrogen has one valence electron, and chlorine has seven valence electrons.

Since SiH2Cl2 has one silicon atom, two hydrogen atoms, and two chlorine atoms, so…

Valence electrons of one silicon atom = 4 × 1 = 4
Valence electrons of two hydrogen atoms = 1 × 2 = 2
Valence electrons of two chlorine atoms = 7 × 2 = 14

And the total valence electrons = 4 + 2 + 14 = 20

• Second, find the total electron pairs

We have a total of 20 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 = 20 ÷ 2 = 10

• Third, determine the central atom

Here hydrogen can not be the central atom. Because the central atom is bonded with at least two other atoms, and hydrogen has only one electron in its last shell, so it can not make more than one bond.

Now we have to choose the central atom from silicon and chlorine. Place the least electronegative atom at the center.

Since silicon is less electronegative than chlorine, assume that the central atom is silicon.

Therefore, place silicon in the center and hydrogen and chlorine on either side.

• And finally, draw the rough sketch

#2 Mention lone pairs on the atoms

Here, we have a total of 10 electron pairs. And four bonds are already marked. So we have to only mark the remaining six electron pairs as lone pairs on the sketch.

Also remember that both (silicon and chlorine) are the period 3 elements, so they can keep more than 8 electrons in their last shell. And hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are hydrogens and chlorines. But no need to mark on hydrogen, because each hydrogen has already two electrons.

So for each chlorine, there are three lone pairs, and for silicon, there is zero lone pair because all six electron pairs are over.

Mark the lone pairs on the sketch as follows:

#3 If needed, mention formal charges on the atoms

Use the following formula to calculate the formal charges on atoms:

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

For silicon atom, formal charge = 4 – 0 – ½ (8) = 0

For each hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0

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

Here, the atoms do not have charges, so no need to mark the charges.

In the above structure, you can see that the central atom (silicon) forms an octet. The outside atoms (chlorines) also form an octet, and all hydrogens form a duet. Hence, the octet rule and duet rule are satisfied.

Therefore, this structure is the stable Lewis structure of SiH2Cl2.

Next: NF5 Lewis structure