# CH2S Lewis structure

CH2S (thioformaldehyde) has one carbon atom, two hydrogen atoms, and one sulfur atom.

In CH2S Lewis structure, there is one double bond and two single bonds around the carbon atom, with one sulfur atom and two hydrogen atoms attached to it. And on the sulfur atom, there are two lone pairs.

Contents

## Steps

Use these steps to correctly draw the CH2S Lewis structure:

#1 First draw a rough sketch
#2 Mark lone pairs on the atoms
#3 Calculate and mark formal charges on the atoms, if required
#4 Convert lone pairs of the atoms, and minimize formal charges
#5 Repeat step 4 if needed, until all charges are minimized, to get a stable Lewis structure

Let’s discuss each step in more detail.

### #1 First draw a rough sketch

• First, determine the total number of valence electrons

In the periodic table, carbon lies in group 14, hydrogen lies in group 1, and sulfur lies in group 16.

Hence, carbon has four valence electrons, hydrogen has one valence electron, and sulfur has six valence electrons.

Since CH2S has one carbon atom, two hydrogen atoms, and one sulfur atom, so…

Valence electrons of one carbon atom = 4 × 1 = 4
Valence electrons of two hydrogen atoms = 1 × 2 = 2
Valence electrons of one sulfur atom = 6 × 1 = 6

And the total valence electrons = 4 + 2 + 6 = 12

• Second, find the total electron pairs

We have a total of 12 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 = 12 ÷ 2 = 6

• 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 carbon and sulfur. Place the least electronegative atom at the center.

Since carbon is less electronegative than sulfur, assume that the central atom is carbon.

Therefore, place carbon in the center and hydrogen and sulfur on either side.

• And finally, draw the rough sketch

### #2 Mark lone pairs on the atoms

Here, we have a total of 6 electron pairs. And three bonds are already marked. So we have to only mark the remaining three electron pairs as lone pairs on the sketch.

Also remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its last shell. Hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell. And sulfur is a period 3 element, so it can keep more than 8 electrons in its last shell.

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

So for sulfur, there are three lone pairs, and for carbon, there is zero lone pair because all three electron pairs are over.

Mark the lone pairs on the sketch as follows:

### #3 Calculate and mark formal charges on the atoms, if required

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

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

For carbon atom, formal charge = 4 – 0 – ½ (6) = +1

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

For sulfur atom, formal charge = 6 – 6 – ½ (2) = -1

Here, both carbon and sulfur atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both carbon and sulfur atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.

### #4 Convert lone pairs of the atoms, and minimize formal charges

Convert a lone pair of the sulfur atom to make a new C — S bond with the carbon atom as follows:

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

Therefore, this structure is the stable Lewis structure of CH2S.

Next: C4H8 Lewis structure