CH3O- Lewis structure

CH₃O^– (methoxide) has one carbon atom, three hydrogen atoms, and one oxygen atom.

In CH₃O^– Lewis structure, there are four single bonds around the carbon atom, with three hydrogen atoms and one oxygen atom attached to it, and on the oxygen atom, there are three lone pairs.

Also, there is a negative (-1) charge on the oxygen atom.

Alternative method: Lewis structure of CH₃O^–

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 CH₃O^– has one carbon atom, three hydrogen atoms, and one oxygen atom, so…

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

Now the CH₃O^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 4 + 3 + 6 + 1 = 14

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 14 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 = 14 ÷ 2 = 7

• 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.

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 7 electron pairs. And four bonds are already marked. So we have to only mark the remaining three electron pairs as lone pairs on the sketch.

Also remember that hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell. And both (carbon and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their 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 carbon atom, formal charge = 4 – 0 – ½ (8) = 0

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

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

Here, the oxygen atom has a charge, so mark it on the sketch as follows:

Final structure

The final structure of CH₃O^– includes a central carbon atom linked to three hydrogen atoms and one oxygen atom through single covalent bonds. In this configuration, the carbon atom satisfies the octet rule by forming four total bonds and possessing no lone pairs. The oxygen atom reaches its stable octet by forming a single bond with the carbon atom and retaining three lone pairs. Within this layout, each hydrogen atom achieves a stable duet. This arrangement represents the most stable state for the ion because the negative formal charge is localized on the more electronegative oxygen atom, while the carbon and hydrogen atoms maintain formal charges of zero. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of the methoxide ion.

To complete the representation, draw square brackets around the entire Lewis structure and place a “-” or “-1” sign as a superscript outside the upper right bracket. This notation signifies that the negative charge is a property of the whole ion.

Next: SCl₆ Lewis structure

External video

• CH3O- Lewis Structure: How to Draw the Lewis Structure for CH3O- – YouTube • Wayne Breslyn

External links

• https://lambdageeks.com/ch3o-lewis-structure/
• https://homework.study.com/explanation/draw-the-lewis-structure-for-ch3o-and-determine-the-formal-charge-of-each-atom.html
• https://www.chegg.com/homework-help/questions-and-answers/give-lewis-dot-structure-ch3o-q1480153
• https://www.numerade.com/ask/question/draw-the-formal-charge-of-each-atom-of-each-atom-of-ch3o-needed-detail-explanation-75363/