The Lewis structure of CH3– contains three single bonds, with carbon in the center, and three hydrogens on either side. There is one lone pair on the carbon atom, and the hydrogen atom does not have any lone pair.
Plus, there is a negative (-1) charge on the carbon atom.
Steps
By using the following steps, you can easily draw the Lewis structure of CH3–.
#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Calculate formal charge and check stability (if octet is already completed on central atom)
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 and hydrogen is a group 1 element. Hence, carbon has four valence electrons and hydrogen has one valence electron.
Now CH3– has one carbon atom and three hydrogen atoms.
So the total number of valence electrons = valence electrons of carbon atom + (valence electrons of hydrogen atom × 3)
And CH3– has a negative (-1) charge, so we have to add one more electron.
Therefore, the total number of valence electrons = 4 + 3 + 1 = 8
- 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.
Hence, assume that carbon is the central atom.
So now, put carbon in the center and hydrogens on either side. And draw the rough skeleton structure for the Lewis structure of CH3– something like this:
Also read: How to draw Lewis structure of NH2– (4 steps)
#2 Show chemical bond
Place two electrons between the atoms to show a chemical bond. Since carbon is surrounded by three hydrogens, use six electrons to show three chemical bonds as follows:
Also read: How to draw Lewis structure of acetone (5 steps)
#3 Mark lone pairs
As calculated earlier, we have a total of 8 valence electrons. And in the above structure, we have already used six valence electrons. Hence, two valence electrons are remaining.
And two valence electrons represent one lone pair.
Note 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.
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. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.
So the central atom (carbon) will get one lone pair.
Now draw the Lewis structure of CH3– something like this:
In the above structure, you can see that the octet is completed on the central atom (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 NI3 (4 steps)
#4 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 carbon atom
Valence electrons = 4
Nonbonding electrons = 2
Bonding electrons = 6
Formal charge = 4 – 2 – ½ (6) = -1
- For each hydrogen atom
Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2
Formal charge = 1 – 0 – ½ (2) = 0
Mention the formal charges of atoms on the structure. So the Lewis structure of CH3– looks something like this:
In the above structure, you can see that the formal charges of atoms are closer to zero. Therefore, this is the most stable Lewis structure of CH3–.
And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.
Now CH3– is an ion having a negative (-1) charge, so draw brackets around the above Lewis structure and mention that charge on the top right corner. And then, the Lewis structure of CH3– looks something like this:
Related
- Lewis structure of NH2–
- Lewis structure of acetone
- Lewis structure of NI3
- Lewis structure of ICl2–
- Lewis structure of HCO3–
External video
- How to Draw the Lewis Structure for CH3- (Methyl anion) – YouTube • Wayne Breslyn
External links
- CH3- Lewis Structure in 6 Steps (With Images) – Pediabay
- What is the Lewis structure for CH3 – Quora
- Chemical Bonding: CH3- Lewis Structure – The Geoexchange
- What is the structure and hybridisation of CH3 – Socratic
- For the lewis structure of CH3-, what is the central atom – Numerade
Deep
Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.