Lewis structure of acetone

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The Lewis structure of acetone (CH₃)₂CO contains one double bond and eight single bonds, with three carbons in the center. The left carbon and right carbon are attached with three hydrogens, and center carbon is attached with one oxygen. There are two lone pairs on the oxygen atom, and carbon atom and hydrogen atom do not have any lone pair.

Steps

By using the following steps, you can easily draw the Lewis structure of acetone.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Complete octet on central atom
#5 Calculate formal charge and check stability

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

• Let’s calculate the total number of valence electrons

We know that… carbon is a group 14 element, hydrogen is a group 1 element, and oxygen is a group 16 element. Hence, carbon has four valence electrons, hydrogen has one valence electron, and oxygen has six valence electrons.

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

So the total number of valence electrons = (valence electrons of carbon atom × 3) + (valence electrons of hydrogen atom × 6) + valence electrons of oxygen atom

Therefore, the total number of valence electrons = 12 + 6 + 6 = 24

• Now decide the central atom

We can not assume hydrogen as 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.

Therefore, choose the central atom from carbon and oxygen.

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for carbon and oxygen as follows:

Electronegativity value of carbon = 2.55
Electronegativity value of oxygen = 3.44

Obviously, carbon is less electronegative than oxygen. Hence, assume that center carbon is the central atom (as there are three carbons).

So now, put three carbons in the center and oxygen and six hydrogens on either side. And draw the rough skeleton structure for the Lewis structure of acetone something like this:

Also read: How to draw Lewis structure of NI₃ (4 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since three carbons are surrounded by oxygen and six hydrogens, use eighteen electrons to show nine chemical bonds as follows:

#3 Mark lone pairs

As calculated earlier, we have a total of 24 valence electrons. And in the above structure, we have already used eighteen valence electrons. Hence, six valence electrons are remaining.

Two valence electrons represent one lone pair. So six valence electrons = three lone pairs.

Note 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.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are hydrogens, oxygen, left carbon, and right carbon. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.

So oxygen will get three lone pairs. And left carbon, right carbon, and central atom (center carbon) will not get any lone pair, because all three lone pairs are used.

Now draw the Lewis structure of acetone something like this:

In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (center carbon) doesn’t form an octet.

So in the next step, we have to complete the octet on the central atom.

Also read: How to draw Lewis structure of ICl₂^– (4 steps)

#4 Complete octet on central atom

Remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Now center carbon already has six valence electrons. Hence, center carbon needs two more valence electrons to complete its octet.

So convert one lone pair from the oxygen atom to make a new bond with the center carbon atom. And then, the Lewis structure of acetone looks something like this:

In the above structure, you can see that the octet is completed on the central atom (center carbon), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

Also read: How to draw Lewis structure of HCO₃^– (5 steps)

#5 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

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

Collect the data from the above structure and then, write it down below as follows:

• For each carbon atom

Valence electrons = 4
Nonbonding electrons = 0
Bonding electrons = 8

Formal charge = 4 – 0 – ½ (8) = 0

• For each hydrogen atom

Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2

Formal charge = 1 – 0 – ½ (2) = 0

• For oxygen atom

Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of acetone looks something like this:

In the above structure, you can see that the formal charges of all atoms are zero. Therefore, this is the stable Lewis structure of acetone.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Related

• Lewis structure of NI₃
• Lewis structure of ICl₂^–
• Lewis structure of HCO₃^–
• Lewis structure of HNO₂
• Lewis structure of I₂

External links

• Lewis Structure for Acetone – The University of Maryland
• Chemical Bonding: Acetone Lewis Structure – The Geoexchange
• Lewis structure of acetone CH3COCH3 – Chemistry Online
• Illustrated Glossary of Organic Chemistry – Acetone – UCLA Chemistry
• C3H6O Lewis Structure (Acetone) – Pinterest
• The formula for acetone is CH3COCH3. In acetone, the second carbon atom is bonded to the oxygen atom and to both of the other carbon atoms. Draw acetone’s Lewis diagram – Homework.Study.com
• Acetone (C3H6O) Lewis Structure in 3 Steps (With Images) – Pediabay
• Draw the Lewis Structure for acetone ((CH3)2(CO) – Chegg
• Example of Lewis structure generation with acetone – ResearchGate
• draw the lewis structure of acetone, (CH3)2CO (C in the middle, with two C’s and an O bonded to it) – Brainly
• C3H6O Lewis Structure, Polarity, Molecular Shape and much more – Geometry of Molecules
• The Lewis structure of acetone needs to be determined – Bartleby
• Acetone Formula & Structure – Purdue University
• Draw the Lewis Structure for acetone ((CH3)2(CO) – Course Hero
• Draw the Lewis structure of acetone, (CH3)2CO – Numerade
• Does protonated acetone have resonance structures? I drew the Lewis dot structure but the carbon’s octet is satisfied – Reddit