Lewis Structure of OCS (With 6 Simple Steps to Draw!)

Ready to learn how to draw the lewis structure of OCS?

Awesome!

Here, I have explained 6 simple steps to draw the lewis dot structure of OCS (along with images).

So, if you are ready to go with these 6 simple steps, then let’s dive right into it!

Lewis structure of OCS contains two double bonds between the Carbon-Oxygen atoms and Carbon-Sulfur atoms. The Carbon atom (C) is at the center and it is surrounded by one Oxygen atom (O) and one Sulfur atom (S). The Carbon atom does not have a lone pair while the Oxygen and Sulfur atoms have 2 lone pairs.

Let’s draw and understand this lewis dot structure step by step.

(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of OCS).

6 Steps to Draw the Lewis Structure of OCS

Step #1: Calculate the total number of valence electrons

Here, the given molecule is OCS. In order to draw the lewis structure of OCS, first of all you have to find the total number of valence electrons present in the OCS molecule.
(Valence electrons are the number of electrons present in the outermost shell of an atom).

So, let’s calculate this first.

Calculation of valence electrons in OCS

• For Oxygen:

Oxygen is a group 16 element on the periodic table. ^[1]

Hence, the valence electron present in oxygen is 6 (see below image).

• For Carbon:

Carbon is a group 14 element on the periodic table. ^[2]

Hence, the valence electrons present in carbon is 4 (see below image).

• For Sulfur:

Sulfur is a group 16 element on the periodic table. ^[3]

Hence, the valence electrons present in sulfur is 6 (see below image).

Hence in a OCS molecule,
Valence electrons given by each Oxygen (O) atom = 6
Valence electrons given by Carbon (C) atom = 4
Valence electrons given by Sulfur (S) atom = 6
So, total number of Valence electrons in OCS molecule = 6 + 4 + 6 = 16

Step #2: Select the center atom

While selecting the atom, always put the least electronegative atom at the center. 

(Remember: Fluorine is the most electronegative element on the periodic table and the electronegativity decreases as we move right to left in the periodic table as well as top to bottom in the periodic table). ^[3]

Here in the OCS molecule, if we compare the oxygen atom (O), carbon atom (C) and sulfur atom (S), then the carbon is less electronegative than oxygen and sulfur.

So, carbon should be placed in the center and the remaining oxygen and sulfur atoms will surround it.

Step #3: Put two electrons between the atoms to represent a chemical bond

Now in the above sketch of OCS molecule, put the two electrons (i.e electron pair) between the atoms to represent a chemical bond between them.

These pairs of electrons present between the Oxygen (O), Carbon (C), and Sulfur (S) atoms form a chemical bond, which bonds these atoms with each other in a OCS molecule.

Step #4: Complete the octet (or duplet) on outside atoms. If the valence electrons are left, then put the valence electrons pair on the central atom

Don’t worry, I’ll explain!

In the Lewis structure of OCS, the outer atoms are oxygen atom and sulfur atom.

So now, you have to complete the octet on these oxygen and sulfur atoms (because they require 8 electrons to have a complete outer shell).

Now, you can see in the above image that both the oxygen and sulfur atoms form an octet.

Also, all the 16 valence electrons of OCS molecule (as calculated in step #1) are used in the above structure. So there are no remaining electron pairs.

Hence there is no change in the above sketch of OCS.

Let’s move to the next step.

Step #5: Check whether the central atom has octet or not. If it does not have an octet, then move the electron pair from the outer atom to form a double bond or triple bond

In this step, we have to check whether the central atom (i.e carbon) has an octet or not. 

In simple words, we have to check whether the central Carbon (C) atom is having 8 electrons or not.

As you can see from the above image, the central atom (i.e carbon) has only 4 electrons. So it does not fulfill the octet rule.

Now, in order to fulfill the octet of carbon atom, we have to move the electron pair from the outer atom (i.e oxygen atom) to form a double bond.

Still, the octet of carbon atom is not fulfilled as it has only 6 electrons.

So again moving the electron pair from the sulfur atom, we will get the following structure.

Now you can see from the above image that the central atom (i.e carbon), is having 8 electrons. So it fulfills the octet rule and the carbon atom is stable.

Step #6: Final step – Check the stability of lewis structure by calculating the formal charge on each atom

Now, you have come to the final step and here you have to check the formal charge on oxygen atom (O), carbon atom (C) as well as sulfur atom (S).

For that, you need to remember the formula of formal charge;

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

• For Oxygen:
  Valence electron = 6 (as it is in group 16)
  Nonbonding electrons = 4
  Bonding electrons = 4
• For Carbon:
  Valence electrons = 4 (as it is in group 14)
  Nonbonding electrons = 0
  Bonding electrons = 8
• For Sulfur:
  Valence electrons = 6 (as it is in group 16)
  Nonbonding electrons = 4
  Bonding electrons = 4

Formal charge	=	Valence electrons	–	Nonbonding electrons	–	(Bonding electrons)/2
O	=	6	–	4	–	4/2	=	0
C	=	4	–	0	–	8/2	=	0
S	=	6	–	4	–	4/2	=	0

So you can see above that the formal charges on oxygen, carbon as well as sulfur are “zero”.

Hence, there will not be any change in the above structure and the above lewis structure of OCS is the final stable structure only.

Each electron pair (:) in the lewis dot structure of OCS represents the single bond ( | ). So the above lewis dot structure of OCS can also be represented as shown below.

Related lewis structures for your practice:
Lewis Structure of Br3-
Lewis Structure of H3O+
Lewis Structure of CH3NO2
Lewis Structure of AsH3
Lewis Structure of SeF6 

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