Trimethylamine (N(CH3)3) has a nitrogen (N) atom with five valence electrons, each bonded to a methyl group (CH3) with one valence electron from carbon (C). The Lewis structure shows three single N-C bonds and a lone pair on nitrogen, totaling 8 electrons around N. The molecular geometry is trigonal pyramidal with bond angles slightly less than 109.5° due to lone pair-bond pair repulsion. The molecule is polar, influenced by the lone pair on nitrogen and the arrangement of methyl groups. The electronegativity of N (3.04) relative to C (2.55) also contributes to its reactivity and interactions.
The present article contains detail information of N(CH3)3 Lewis Structure. N(CH3)3 exists as a gas at room temperature. It is an organic compound which possess a fish-like odor.
The Lewis structure of N(CH3)3 consists of central atom nitrogen and three methyl groups surrounding the central atom. There is a lone pair on central atom nitrogen in the Lewis structure of Trimethylamine.
| Molecular formula | N(CH3)3 or C3H9N |
| Chemical Name | Trimethylamine N,N-Dimethylmethanamine |
| Lone pairs on the central atom | 1 |
| Number of valence electrons in N(Ch3)3 | 26 |
| Molecular Geometry of N(CH3)3 | Trigonal pyramidal |
| Electron Geometry of N(CH3)3 | Tetrahedral |
| Bond Angle C-N-C | 108 degrees |
| Resonance Effect | Do not show resonance |
| Octet Rule | Follows the octet Rule |
| Formal charge | 0 |
| Hybridisation of the central atom | Sp3 |
| Polar or non-polar | Polar |
| Solubility in water | Soluble in water |
| Acidic or basic | Basic |
| symmetric Or Asymmetric | Asymmetric |
Valence electrons in N(CH3)3 Lewis structure
In the Lewis structure of Trimethylamine the central Nitrogen atom, Carbon and the hydrogen atom has 5,4 and 1 electron respectively.
| Types of atoms | Valence electrons | Number of atoms | Valence electrons in N(CH3)3 |
| Nitrogen | 5 | 1 | 5*1 = 5 |
| Carbon | 4 | 3 | 4*3 = 12 |
| Hydrogen | 9 | 1 | 9*1 = 9 |
| 26 |
so, the number of valence electrons in Lewis N(CH3)3 is 26
How to draw N(CH3)3 Lewis structure?
Lewis structures are the drawings which show the patterns of bonding in the compound. These structures show the number of bonding and also the number of non-bonding electrons present in the compound.
Lewis structure of N(CH3)3 can be drawn in the following steps –
Step 1: Calculate the number of valence electrons
Valence electrons in central atom nitrogen, carbon and hydrogen are 5,4 and 1 respectively.
| Types of atoms | Valence ele ctrons | Number of atoms | Valence electrons in N(CH3)3 |
| Nitrogen | 5 | 1 | 5*1 = 5 |
| Carbon | 4 | 3 | 4*3 = 12 |
| Hydrogen | 9 | 1 | 9*1 = 9 |
| 26 |
So, the number of valence electrons in Trimethylamine is 26.
Step 2: Find out the central atom
Central atom in the Lewis structure.is usually the atom which has lowest subscript in the compound so Nitrogen is the central atom in N(CH3)3.
The skeletal structure of N(CH3)3 is –
Step 3: Place a bond or a electron pair between Nitrogen and Carbon atoms and also Carbon and Hydrogen atoms
Nitrogen forms 3 bonds with 3 carbon atoms in N(CH3)3 Lewis structure.
Step 4: Complete octet of central Nitrogen atom
After completing the octet of the central atom, we see that the central nitrogen atom has a lone pair of electrons.
Step 5: Check for the stability of the Lewis structure by finding out the formal charge on atoms in N(CH3)3
Formula for formal charge:
Formal charge = valence electrons – 0.5*bonding electrons – non-bonding electrons
Formal charge on nitrogen:
Formal charge = 5 – 0.5*6 – 2
= 0
The formal charge on nitrogen is 0
Formal charge on carbon atom:
Formal charge = 4 – 0.5*8 – 0
= 0
Formal charge on carbon is 0
Formal charge on hydrogen atom:
Formal charge = 1 – 0.5*2 – 0
= 0
Formal charge on hydrogen is 0
As the formal charge on all the atoms in N(CH3)3 is 0
So, we have got our perfect Lewis structure.
How many lone pairs are present in the Lewis structure of N(CH3)3?
Formula to find the lone pairs are –
Lone pairs = 0.5*(Valence Electrons of central atom– Number of atoms attached to the central atom)
= 0.5*(5 – 3)
= 1
So, the number of lone pair present on the central Nitrogen atom is 1.
Does N(CH3)3 follow the octet rule?
N(CH3)3 contains 26 valence electrons. All the atoms in N(CH3)3 have completed their octet as can be seen from the Lewis structure of N(CH3)3. Thus, N(CH3)3 follows the octet rule.
Formal Charge on each atom in the Lewis structure of N(CH3)3
Formula for formal charge:
Formal charge = valence electrons – 0.5*bonding electrons – non-bonding electrons
Formal charge on nitrogen:
Formal charge = 5 – o.5*6 – 2
= 0
The formal charge on nitrogen is 0
Formal charge on carbon atom:
Formal charge = 4 – 0.5*8 – 0
= 0
Formal charge on carbon is 0
Formal charge on hydrogen atom:
Formal charge = 1 – 0.5*2 – 0
= 0
Why is the C-N-C bond angle in N(CH3)3 is 108 degrees?
Due to the repulsion between the lone pair present on the central nitrogen atom and bonded pairs the tetrahedral angle decreases in trimethylamine from 109.5 degrees to 108 degrees.
What is the hybridization of Nitrogen in N(CH3)3?
Hybridization of central atom can be found out by using the formula –
Hybridization number = number of atoms attached to the central atom + number of lone pairs present on the central atom
Hybridization Number for Nitrogen in N(CH3)3 = 3 + 1 = 4
so hybridization of central atom nitrogen in N(CH3)3 is sp3.
What is molecular and electron geometry of N(CH3)3 compound?
We know that hybridization of the central atom in N(CH3)3 is sp3 and 1 lone pair is present on the central atom Nitrogen
So according to AXnEx notation of VSEPR theory,
Where –
A is for the central atom
X is for the surrounding atoms, n is number of surrounding atoms
E is for the lone pairs on the central atom, x is for the number of lone pairs.
AXnEx notation for N(CH3)3 is AX3E1 as nitrogen is bonded to three methyl groups and it has a lone pair on it.
Now, AX3E1 notation corresponds to Molecular geometry as Trigonal Pyramidal and Electron Geometry as Tetrahedral in accordance with the VSEPR Chart.
| Total Domains | General Formula | Bonded atoms | Lone Pairs | Molecular Shape | Electron Geometry |
| 1 | AX | 1 | 0 | Linear | Linear |
| 2 | AX2 | 2 | 0 | Linear | Linear |
| AXE | 1 | 1 | Linear | Linear | |
| 3 | AX3 | 3 | 0 | Trigonal Planar | Trigonal Planar |
| AX2E | 2 | 1 | Bent | Trigonal Planar | |
| AXE2 | 1 | 2 | Linear | Trigonal Planar | |
| 4 | AX4 | 4 | 0 | Tetrahedral | Tetrahedral |
| AX3E | 3 | 1 | Trigonal Pyramid | Tetrahedral | |
| AX2E2 | 2 | 2 | Bent | Tetrahedral | |
| AXE3 | 1 | 3 | Linear | Tetrahedral |
so the molecular geometry of N(CH3)3 is Trigonal Pyramidal and the Electron geometry is Tetrahedral.
Why is N(CH3)3 a weak base?
N(CH3)3 is a weak base because of presence of bulky methyl groups around the central nitrogen atoms which makes it difficult for the proton to approach for bonding.
Why is Trimethylamine a polar compound?
Electronegativity of Nitrogen is 3.0 and carbon is 2.5
A molecule is said to be polar when the difference in the electronegativity of its atoms is greater than 0.4
The difference in electronegativity of Nitrogen and Carbon is 0.5
This means that N(CH3)3 has positive and negative ends. This makes N(CH3)3 molecule polar in nature.
Is N(CH3)3 symmetrical or asymmetrical?
N(CH3)3 (Trimethylamine) is asymmetrical molecule as it is a polar molecule and contains positive and negative ends.
Is N(CH3)3 linear?
No, N(CH3)3 is trigonal pyramidal in shape.
Why does N(CH3)3 compound not show resonance?
- Resonance is shown by such compounds in which there is a possibility for the delocalization of electrons.
In N(CH3)3, the lone pair is localized on the central atom Nitrogen.
- For showing resonance, all atoms should lie in one plane. In N(CH3)3, the nitrogen is sp3 hybridized so all atoms do not lie in one plane.
That’s why N(CH3)3 compound does not show resonance.
Is N(CH3)3 tetrahedral?
Yes, the electron geometry of N(CH3)3 is tetrahedral as for electron geometry we consider both the bonded atoms as well as the lone pairs
Conclusion:
In a nutshell, N(CH3)3 is a polar compound. The molecular geometry of N(CH3)3 is Trigonal Pyramidal while the Electron Geometry is Tetrahedral. N(CH3)3 is basic in nature.
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Hi…I am Sonali Jham. I have done my Post-Graduation in Chemistry and also completed B. Ed. I am a Teacher and a Dietician by profession.
My hobby is reading and painting.
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