CH3- Lewis structure

CH₃^– (methanide) has one carbon atom and three hydrogen atoms.

In the CH₃^– Lewis structure, there are three single bonds around the carbon atom, with three hydrogen atoms attached to it, and on the carbon atom, there is one lone pair.

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

Alternative method: Lewis structure of CH₃^–

Rough sketch

• First, determine the total number of valence electrons

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

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

Since CH₃^– has one carbon atom and three hydrogen atoms, so…

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

Now the CH₃^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 4 + 3 + 1 = 8

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

• Second, find the total electron pairs

We have a total of 8 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 = 8 ÷ 2 = 4

• 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.

Hence, here we have to assume that the central atom is carbon.

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 4 electron pairs. And three C — H bonds are already marked. So we have to only mark the remaining one electron pair as a lone pair 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. 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. But no need to mark on hydrogen, because each hydrogen has already two electrons.

So for carbon, there is one lone pair.

Mark the lone pair 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 – 2 – ½ (6) = -1

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

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

Final structure

The final structure of CH₃^– consists of a central carbon atom linked to three hydrogen atoms through single covalent bonds. In this configuration, the carbon atom satisfies the octet rule by forming three bonds and maintaining one lone pair. Within this layout, each of the three hydrogen atoms achieves its stable duet state through its respective single shared bond. This arrangement represents the most stable state for the ion because it results in a formal charge of -1 on the carbon atom, while all hydrogen atoms carry a formal charge of zero. Accordingly, this specific electronic distribution serves as the definitive and most accurate Lewis representation of this ion.

To properly represent this as an ion, the entire Lewis structure is enclosed within square brackets. The overall charge of 1- is then written as a superscript outside the brackets at the top right, indicating that the structure possesses one additional electron beyond the valence count of the neutral atoms.

Next: I₂ Lewis structure

External video

• How to Draw the Lewis Structure for CH3- (Methyl anion) – YouTube • Wayne Breslyn

External links

• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/CH3–lewis-structure.html
• https://socratic.org/questions/what-is-the-structure-and-hybridisation-of-ch3