I’m super excited to teach you the lewis structure of CH3- ion in just 6 simple steps.
Infact, I’ve also given the step-by-step images for drawing the lewis dot structure of CH3- ion.
So, if you are ready to go with these 6 simple steps, then let’s dive right into it!
Lewis structure of CH3- ion contains three single bonds between each Carbon (C) and Hydrogen (H) atoms. The Carbon atom (C) is at the center and it is surrounded by 3 Hydrogen atoms (H). The carbon atom has 1 lone pair and it has -1 formal charge.
Let’s draw and understand this lewis dot structure step by step.
(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of CH3- ion).
6 Steps to Draw the Lewis Structure of CH3-
Step #1: Calculate the total number of valence electrons
Here, the given ion is CH3- ion. In order to draw the lewis structure of CH3- ion, first of all you have to find the total number of valence electrons present in the CH3- ion.
(Valence electrons are the number of electrons present in the outermost shell of an atom).
So, let’s calculate this first.
Calculation of valence electrons in CH3-
- For Carbon:
Carbon is a group 14 element on the periodic table. 
Hence, the valence electrons present in carbon is 4 (see below image).
- For Hydrogen:
Hydrogen is a group 1 element on the periodic table. 
Hence, the valence electron present in hydrogen is 1 (see below image).
Hence in a CH3- ion,
Valence electrons given by Carbon (C) atom = 4
Valence electron given by each Hydrogen (H) atom = 1
Electron due to -1 charge, 1 more electron is added
So, total number of Valence electrons in CH3- ion = 4 + 1(3) + 1 = 8
Step #2: Select the center atom (H is always outside)
While selecting the center atom, always put the least electronegative atom at the center.
(Remember: Fluorine is the most electronegative element on the periodic table and the electronegativity decreases as we move right to left in the periodic table as well as top to bottom in the periodic table). 
Here in the CH3- ion, if we compare the carbon atom (C) and hydrogen atom (H), then hydrogen is less electronegative than carbon. But as per the rule, we have to keep hydrogen outside.
So, carbon should be placed in the center and the remaining 3 hydrogen atoms will surround it.
Step #3: Put two electrons between the atoms to represent a chemical bond
Now in the above sketch of CH3 molecule, put the two electrons (i.e electron pair) between each carbon atom and hydrogen atom to represent a chemical bond between them.
These pairs of electrons present between the Carbon (C) and Hydrogen (H) atoms form a chemical bond, which bonds the carbon and hydrogen atoms with each other in a CH3 molecule.
Step #4: Complete the octet (or duplet) on outside atoms. If the valence electrons are left, then put the valence electrons pair on the central atom
Don’t worry, I’ll explain!
In the Lewis structure of CH3, the outer atoms are hydrogen atoms.
So now, you have to check whether these hydrogen atoms are forming a duplet or not! (because hydrogen requires only 2 electrons to have a complete outer shell).
You can see in the above image that all the hydrogen atoms form a duplet.
Also, only 6 valence electrons of CH3- ion are used in the above structure.
But there are total 8 valence electrons in CH3- ion (as calculated in step #1).
So the number of electrons left to be kept on the central atom = 8 – 6 = 2.
So let’s keep these two electrons (i.e electron pair) on the central atom.
Now, let’s move to the next step.
Step #5: Check whether the central atom has octet or not
In this step, we have to check whether the central atom (i.e carbon) has an octet or not.
In simple words, we have to check whether the central Carbon (C) atom is having 8 electrons or not.
As you can see from the above image, the central atom (i.e carbon), is having 8 electrons. So it fulfills the octet rule and the carbon atom is stable.
Step #6: Final step – Check the stability of lewis structure by calculating the formal charge on each atom
Now, you have come to the final step and here you have to check the formal charge on carbon atom (C) as well as each hydrogen atom (H).
For that, you need to remember the formula of formal charge;
Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2
- For Carbon:
Valence electrons = 4 (as it is in group 14)
Nonbonding electrons = 2
Bonding electrons = 6
- For Hydrogen:
Valence electron = 1 (as it is in group 1)
Nonbonding electrons = 0
Bonding electrons = 2
|Formal charge||=||Valence electrons||–||Nonbonding electrons||–||(Bonding electrons)/2|
So you can see above that the formal charges on carbon is -1 and the formal charge on the hydrogen atoms is 0.
Let’s keep these charges on the atoms in the above lewis structure of CH3.
As you can see in the above sketch, there is one -ve charge on the carbon atom, which indicates the -1 formal charge on the CH3 molecule.
Hence, the above lewis structure of CH3- ion is the stable lewis structure.
Each electron pair (:) in the lewis dot structure of CH3- ion represents the single bond ( | ). So the above lewis dot structure of CH3- ion can also be represented as shown below.
Related lewis structures for your practice:
Lewis structure of I2
Lewis structure of ICl3
Lewis structure of NOF
Lewis structure of ClF5
Lewis structure of IF4-