To draw the Lewis structure for carbon monosulfide (CS), we start by determining the total number of valence electrons. Carbon (C) has 4 valence electrons and sulfur (S) has 6 valence electrons, so for CS, we have:
- Valence electrons from C: 4
- Valence electrons from S: 6
Adding these together, we get a total of 10 valence electrons to work with.
Next, we place the carbon atom in the center as it is less electronegative than sulfur:
Step 1: Place C and S atoms together.
Step 2: Begin by forming a single bond between C and S. A single bond accounts for 2 electrons:
C - S
Now we have used 2 out of the 10 total electrons, leaving us with 8 electrons.
Step 3: Complete the octet of the sulfur atom by adding 6 more electrons (3 lone pairs) around S:
..
:C - S:
..
Now S has 8 electrons around it (6 lone pair + 2 from the bond).
Step 4: Carbon only has 2 electrons from the bond at this point, so we need to ensure it also achieves an octet. We can achieve this by converting one of the lone pairs from sulfur into a double bond:
..
:C = S:
..
Now both C and S have 8 electrons around them. The final Lewis structure for carbon monosulfide is:
..
:C = S:
..
In this structure, carbon is forming a double bond with sulfur, satisfying the octet rule for both atoms. That’s how we get the Lewis structure for CS!