Carbon disulfide or CS2 is one of the very common molecules we come across while studying chemistry.
If you have ever come across the formation of carbon tetrachloride, a well-known reaction while studying chlorine, you have heard about CS2.
Now let us learn about this sulfide in a detailed manner.
Carbon disulfide (CS2) is a flammable, and highly odorous( not tolerable) molecule in liquid form.
It is usually colorless and volatile that can cause a lot of poisonous outcomes.
From liver and kidney diseases to weight loss and vision impairment, exposure to CS2 is not desirable.
Used as a solvent for iodine and phosphorus, it has a boiling point of 46.24 0C and a density of 1.539 g/cc.
It can be used for the production of viscose rayon and cellophane.
It is also utilized as pesticides and adhesives.
Now let us move below to deeply study the concepts like lewis structure, molecular geometry, hybridization of the CS2 molecule.
Lewis Structure of CS2
If you are a student of chemistry, it is almost obvious that you are aware of the term ‘Lewis Structure”. If not, here’s a brief explanation of the above-mentioned topic.
Lewis Structure is one of the key terminologies to understand the chemical bonding of a molecule since it represents the molecular structure.
It depends on the octet rule concept and is an extension of the electron dot diagram.
Thus, to have a comprehensive idea about CS2 Lewis Structure, let us go through each step clearly and systematically.
The very first step towards drawing the structure of a molecule is to decipher the total number of valence electrons. (A valence electron is a name given to the outer shell electron of an atom that takes part in the creation of a chemical bond).
A very important point to be noted here is the role of the signs ‘+’ and ‘-’. While the positive ‘+’ sign indicates the loss of electrons i.e loss of negative charge, the negative ‘-’ sign is to denote the gain of electrons.
The second step is based on finding the central atom of the molecule. Usually, the one with the highest valence i.e. bonding sites ( in other words, least electronegative) is the central atom.
We can determine the electronegativity value by browsing through the periodic table. As per the trend, it is likely to decrease down a group.
Now, we need to draw a skeleton diagram having the presence of single bonds.
Next, our task is to complete the octet of the atoms around each of the outer ones with the remaining electrons. The advisable decision is to finish the electronegative ones first before starting with the electropositive atoms.
In this step, we have to check whether there are bonds left to be formed. If there is a requirement of multiple bond formation, we have to create double or triple bonds as per requirements to fulfill the octet rule.
The final step of Lewis diagram formation is to verify whether all the atoms are in their lowest possible formal charge.
(A formal charge, also abbreviated as FC is the charge that is assigned to an atom of a molecule when we assume that chemical bonds are always shared equally between atoms inside a molecule.)
Here is how we can easily calculate the formal charge:
Let us know see how we can draw the Lewis Structure for CS2
1. Carbon belongs to Group 4 of the periodic table.
Therefore, the number of valence electrons in the Carbon atom =4.
Sulfur(S) belonging to Group 6 has 6 valence electrons.
CS2 has two S atoms, hence, the valence electrons in sulfur here are 6*2=12.
Total valence electrons is CS2 = 12+4 = 16.
2. According to Step 2, carbon is the least electronegative having the highest bonding sites. C is the central atom here.
3. The skeleton diagram of CS2 is drawn below.
4. We can check and find out that both the sulfur atoms have fulfilled their octet rule here. But, carbon is the only one left with only four electrons surrounding it.
We can easily mend this issue by sharing the electrons around sulfur and bringing them alongside carbon, thus 2 valence electrons from each sulfur atom towards carbon will solve the problem here.
5. We are therefore changing the lone pairs into double bonds as per necessity.
6. Now, we need to check the formal charge following the given mentioned formula.
This is how we draw a complete Lewis Structure of Carbon disulfide.
Hybridization of CS2
Carbon disulfide has sp hybridization.
Now, what is hybridization? Do you know that atoms use hybrid orbitals and not atomic orbitals to form chemical bonds in a molecule?
This process of hybridization is one of the vital concepts of bonding and can be explained in two different methods- one with the help of theory and the other one depending on formulae.
Let us first make you go through the theoretical standpoint to make things easier!
An ‘s’ orbital will overlap with a ‘p’ orbital to create sp hybridization.
If a central atom( here C) has two valence electron density regions surrounding it, then it exhibits sp hybridization.
C ground state configuration: 1s2 2s2 2p2
S ground state configuration: 1s2 2s2 2p6 3s2 3p4
Just in the above section, while discussing the Lewis Structure we learned that in CS2 two double bonds are formed and eight of the 16 valence electrons are used up for this purpose.
The electrons of 2s and 2p orbitals of C form the double bonds and thus they result in sp hybridization.
Here is a formula that can calculate the hybridization value
Here, H: hybridization value
M: valence electron no.
C: charge of the cations
A: charge of the anions
Therefore, H=2 here. It signifies that the hybridization type is sp.
Also, we can calculate the steric number.
Steric Number= No of sigma bonds + No of pi lone pairs( of the central atom, here Carbon).
The octet has been fulfilled by the help of sharing valence electrons among the two sulfur and the carbon atoms, therefore here there is no lone pair.
There are two sigma bonds formed, thus steric number=2, sp hybridization.
Molecular Geometry of CS2
As discussed earlier, CS2 has a linear shape. Here, the bond angles form an angle of 180 degrees.
To determine the molecular geometry of a molecule, we need to get familiar with a concept called VSEPR theory.
Now, what is the VSEPR theory?
VSEPR Theory is the short form for Valence Shell Electron Pair Repulsion Theory.
It is based on the minimum repulsion concept where valence electron pairs that repel each other will form the arrangement or structure that will justify the least repulsion.
Below is the chart that you can refer to find the geometry of different types of molecules.
When any compound has a formula similar to the generic one AX2, it means that X is the bonded atom, and the molecule will have 0 lone pairs and 2 bond pairs.
Thus, in the case of CS2, Sulfur is the bonded atom.
Polarity of CS2
Before we discuss whether CS2 is polar or non-polar, let us just check a concise definition of polarity.
Polarity is basically defined as the condition of having both positive and negative charges i.e. it denotes the distribution of electric charges across the atoms or molecule of a compound.
A polar molecule will result due to unequal sharing of electrons whereas non-polar ones are neutral.
Now, coming to carbon disulfide structure, we already are accustomed to the diagrammatical representation of the molecule.
From there, we can decipher that it is a linear molecule, thus the valence electrons around sulfur and carbon are spread equally with no sulfur having a higher influence on carbon than the other one.
Since there is no pole, hence CS2 is non-polar.
For the detailed reasons of the polarity of CS2, you can also refer to the polarity of CS2.
Understanding of any molecule requires a deep knowledge intake of the internal chemistry and bonding structure.
Here, we have covered the Lewis Structure, Hybridization, Polarity, and Molecular Geometry of Carbon Disulfide in a well-explained and elaborative manner. This will help you grasp the basic concepts in a clear format.
Apart from this, if you want to learn more, you can always read more books and surf a little more.