The Lewis structure of CH3NH2 contains six single bonds, with carbon and nitrogen in the center, and five hydrogens on either side. There is one lone pair on the nitrogen atom, and carbon atom and hydrogen atom do not have any lone pair.
Steps
By using the following steps, you can easily draw the Lewis structure of CH3NH2:
#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, hydrogen is a group 1 element, and nitrogen is a group 15 element. Hence, carbon has four valence electrons, hydrogen has one valence electron, and nitrogen has five valence electrons.
Now CH3NH2 has one carbon atom, five hydrogen atoms, and one nitrogen atom.
So the total number of valence electrons = valence electrons of carbon atom + (valence electrons of hydrogen atom × 5) + valence electrons of nitrogen atom
Therefore, the total number of valence electrons = 4 + 5 + 5 = 14
- 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.
Therefore, choose the central atom from carbon and nitrogen.
The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for carbon and nitrogen as follows:
Electronegativity value of carbon = 2.55
Electronegativity value of nitrogen = 3.04
Obviously, carbon is less electronegative than nitrogen. Hence, assume that carbon is the central atom.
So now, put carbon in the center and nitrogen and five hydrogens on either side. And draw the rough skeleton structure for the Lewis structure of CH3NH2 something like this:
Also read: How to draw Lewis structure of CH3Cl (4 steps)
#2 Show chemical bond
Place two electrons between the atoms to show a chemical bond. Since carbon is surrounded by nitrogen and five hydrogens, use twelve electrons to show six chemical bonds as follows:
Also read: How to draw Lewis structure of SiO2 (5 steps)
#3 Mark lone pairs
As calculated earlier, we have a total of 14 valence electrons. And in the above structure, we have already used twelve valence electrons. Hence, two valence electrons are remaining.
And two valence electrons represent one lone pair.
Note that both (carbon and nitrogen) are the period 2 elements, so they can not keep more than 8 electrons in their 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 and nitrogen. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.
So nitrogen will get one lone pair. And the central atom (carbon) will not get any lone pair, because all lone pairs are used.
Now draw the Lewis structure of CH3NH2 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 ethanol (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 = 0
Bonding electrons = 8
Formal charge = 4 – 0 – ½ (8) = 0
- For each hydrogen atom
Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2
Formal charge = 1 – 0 – ½ (2) = 0
- For nitrogen atom
Valence electrons = 5
Nonbonding electrons = 2
Bonding electrons = 6
Formal charge = 5 – 2 – ½ (6) = 0
Mention the formal charges of atoms on the structure. So the Lewis structure of CH3NH2 looks something like this:
In the above structure, you can see that the formal charges of all atoms are zero. Therefore, this is the stable Lewis structure of CH3NH2.
And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.
Related
- Lewis structure of CH3Cl
- Lewis structure of SiO2
- Lewis structure of ethanol
- Lewis structure of N2H4
- Lewis structure of HBr
External links
- Chemical Bonding: CH3NH2 Lewis Structure – The Geoexchange
- CH3NH2 Lewis Structure in 6 Steps (With Images) – Pediabay
- CH3NH2 Lewis structure, molecular geometry, hybridization, bond angle – Topblogtenz
- CH3NH2 Lewis structure, Hybridization, Molecular Geometry, and Bond angle – Geometry of Molecules
- CH3NH2 Lewis Structure, Molecular Geometry, Hybridization, and Polarity – Techiescientist
- Draw the Lewis structure for CH3NH2. How many sigma and pi bonds does it have? How many bond pairs and lone pairs are there? – Homework.Study.com
- CH3NH2 Lewis Structure (Methylamine) – Pinterest
- CH3NH2 Lewis Structure, Geometry – Kemicalinfo
- Lewis Dot of Methylamine CH3NH2 – Kent’s Chemistry
- Draw a Lewis structure of CH3NH2 (skeletal structure H3CNH2) – Chegg
- CH3NH2 Lewis Structure, Molecular Geometry, Hybridization, Polar or Nonpolar – Studocu
- What is the molecular geometry of CH3NH2? – Quora
- ch3nh2 lewis structure.jpg – Course Hero
- What is the molecular geometry about nitrogen in ch3nh2? – Brainly
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.