SiH3- Lewis Structure in 6 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

SiH3- lewis structure has a Silicon atom (Si) at the center which is surrounded by three Hydrogen atoms (H). There are 3 single bonds between the Silicon atom (Si) and each Hydrogen atom (H). The Silicon atom (Si) has 1 lone pair as well as it has a -ve formal charge.

If you haven’t understood anything from the above image of SiH3- lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of SiH3- ion.

So let’s move to the steps of drawing the lewis structure of SiH3- ion.

Steps of drawing SiH3- lewis structure

Step 1: Find the total valence electrons in SiH3- ion

In order to find the total valence electrons in SiH3- ion, first of all you should know the valence electrons present in silicon atom as well as hydrogen atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of silicon as well as hydrogen using a periodic table.

Total valence electrons in SiH3- ion

→ Valence electrons given by silicon atom:

Silicon is a group 14 element on the periodic table. ^[1] Hence the valence electrons present in silicon is 4.

You can see the 4 valence electrons present in the silicon atom as shown in the above image.

→ Valence electrons given by hydrogen atom:

Hydrogen is group 1 element on the periodic table. ^[2] Hence the valence electron present in hydrogen is 1.

You can see that only 1 valence electron is present in the hydrogen atom as shown in the above image.

Hence, 

Total valence electrons in SiH3- ion = valence electrons given by 1 silicon atom + valence electrons given by 3 hydrogen atoms + 1 more electron is added due to 1 negative charge = 4 + 1(3) + 1 = 8.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

(Remember: If hydrogen is present in the given molecule, then always put hydrogen outside.)

Now here the given ion is SiH3- ion and it contains silicon atom (Si) and hydrogen atoms (H).

You can see the electronegativity values of silicon atom (Si) and hydrogen atom (H) in the above periodic table.

If we compare the electronegativity values of silicon (Si) and hydrogen (H) then the hydrogen atom is less electronegative. But as per the rule we have to keep hydrogen outside.

So here the silicon atom (Si) is the center atom and the hydrogen atoms (H) are the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the SiH3 molecule, you have to put the electron pairs between the silicon atom (Si) and hydrogen atoms (H).

This indicates that the silicon (Si) and hydrogen (H) are chemically bonded with each other in a SiH3 molecule.

Step 4: Make the outer atoms stable

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of SiH3 molecule, you can see that the outer atoms are hydrogen atoms.

These outer hydrogen atoms are forming a duplet and hence they are stable.

Also, in step 1 we have calculated the total number of valence electrons present in the SiH3- ion.

The SiH3- ion has a total 8 valence electrons and out of these, only 6 valence electrons are used in the above sketch.

So the number of electrons which are left = 8 – 6 = 2.

You have to put these 2 electrons on the central silicon atom in the above sketch of SiH3 molecule.

Now let’s proceed to the next step.

Step 5: Check the octet on the central atom

In this step, you have to check whether the central silicon atom (Si) is stable or not.

In order to check the stability of the central silicon (Si) atom, we have to check whether it is forming an octet or not.

You can see from the above picture that the silicon atom is forming an octet. That means it has 8 electrons.

And hence the central silicon atom is stable.

Now let’s proceed to the final step to check whether the lewis structure of SiH3 is stable or not.

Step 6: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of SiH3 molecule.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on silicon (Si) atom as well as hydrogen (H) atoms present in the SiH3 molecule.

For calculating the formal charge, you have to use the following formula;

Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons

You can see the number of bonding electrons and nonbonding electrons for each atom of SiH3 molecule in the image given below.

For Silicon (Si) atom:
Valence electrons = 4 (because silicon is in group 14)
Bonding electrons = 6
Nonbonding electrons = 2

For Hydrogen (H) atom:
Valence electron = 1 (because hydrogen is in group 1)
Bonding electrons = 2
Nonbonding electrons = 0

From the above calculations of formal charge, you can see that the silicon (Si) atom has -1 charge, while the hydrogen atoms have 0 charges.

So let’s keep these charges on the respective atoms in the SiH3 molecule.

This overall -1 charge on the SiH3 molecule is represented in the image given below.

In the above lewis dot structure of SiH3- ion, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of SiH3- ion.

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

About author

Jay Rana

Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. He is a founder of Pediabay and is passionate about helping students through his easily digestible explanations.

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