Acetone Lewis structure

(CH₃)₂CO or C₃H₆O (acetone) has three carbon atoms, six hydrogen atoms, and one oxygen atom.

In the acetone Lewis structure, there are two single bonds between the three carbon atoms. The left carbon and right carbon are attached with three hydrogen atoms, and the center carbon makes a double bond with one oxygen atom. And on the oxygen atom, there are two lone pairs.

Alternative method: Lewis structure of acetone

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 oxygen lies in group 16.

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

Since ethanol (C₃H₆O) has three carbon atoms, six hydrogen atoms, and one oxygen atom, so…

Valence electrons of three carbon atoms = 4 × 3 = 12
Valence electrons of six hydrogen atoms = 1 × 6 = 6
Valence electrons of one oxygen atom = 6 × 1 = 6

And the total valence electrons = 12 + 6 + 6 = 24

Learn how to find: Carbon valence electrons, Hydrogen valence electrons, and Oxygen valence electrons

• Second, find the total electron pairs

We have a total of 24 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 = 24 ÷ 2 = 12

• 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 oxygen. Place the least electronegative atom at the center.

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

Here, there are three carbon atoms, so we can assume any one as the central atom.

Let’s assume that the central atom is center carbon.

Therefore, place carbons in the center and hydrogen and oxygen on either side.

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 12 electron pairs. And nine bonds are already marked. So we have to only mark the remaining three electron pairs as lone pairs on the sketch.

Also remember that both (carbon and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell. And hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell.

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

So for oxygen, 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:

Formal charge

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

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

For left carbon and right carbon atom, formal charge = 4 – 0 – ½ (8) = 0

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

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

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

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

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

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

Final structure

The final structure of C₃H₆O consists of a central carbon atom double-bonded to an oxygen atom and single-bonded to two outer carbon atoms. In this arrangement, the central carbon satisfies the octet rule through its three bonding neighbors, while the oxygen atom fulfills its octet by maintaining two lone pairs alongside the double bond. Each of the two outer carbon atoms is single-bonded to three hydrogen atoms, ensuring every carbon atom has four bonds and every hydrogen reaches its stable duet. This configuration is the most stable because it results in formal charges of zero for all atoms involved, representing the most energetically favorable state for the molecule. As a result, this specific electronic distribution serves as the definitive and most accurate Lewis representation of acetone.

Next: HCO₃^– Lewis structure

External video

• How to Draw the Lewis Dot Structure for (CH3)2CO: Acetone – YouTube • Wayne Breslyn

External links

• https://lambdageeks.com/acetone-lewis-structure/
• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/Acetone-lewis-structure.html
• https://geometryofmolecules.com/c3h6o-lewis-structure-polarity-molecular-shape/