Lewis structure of CH3+

CH₃⁺ (methenium) has one carbon atom and three hydrogen atoms.

In the Lewis structure of CH₃⁺, there are three single bonds around the carbon atom, with three hydrogen atoms attached to it, and none of the atoms has a lone pair.

Also, there is a positive (+1) charge on the carbon atom.

Alternative method: CH₃⁺ Lewis structure

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 positive (+1) charge, so we have to subtract one electron.

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

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

• Second, find the total electron pairs

We have a total of 6 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 = 6 ÷ 2 = 3

• 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 3 electron pairs. And three C — H bonds are already marked. So we do not have to mark any electron pair as a lone pair on the sketch.

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 (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 forms three total bonds and possesses no lone pairs, resulting in six valence electrons around the central atom. Within this layout, each hydrogen atom achieves a stable duet. This arrangement represents the most stable state for the ion because it allows for the most symmetrical distribution of electron density despite the electron-deficient nature of the carbon. Accordingly, this specific electronic distribution serves as the definitive and most accurate Lewis representation of the methyl cation.

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 positive charge is a property of the whole ion.

Next: CH₂CHCN Lewis structure

External video

• CH3+ Lewis Structure: How to Draw the Lewis Structure for CH3+ – YouTube • Wayne Breslyn