Nitrogen trichloride (NCl3) lewis dot structure, molecular geometry, polar or non-polar, hybridization
Nitrogen trichloride is a very explosive substance that appears like an oily liquid with the chemical formula NCl3. It smells similar to chlorine. It has a dipole moment of 0.6 D that shows it is moderately polar.
In this article, we will discuss Nitrogen trichloride (NCl3) lewis dot structure, molecular geometry, polar or non-polar, hybridization, its bond angle, etc.
In pure concentration, nitrogen trichloride becomes the most dangerous explosive substance due to the difference between chlorine and nitrogen in terms of size that give the unstable product.
Properties of Nitrogen trichloride
It has an odor like chlorine.
It is not soluble in water but soluble in benzene, PCl3, CCl4, etc.
It has a melting point of −40°C and a boiling point of 71°C.
How to draw Nitrogen trichloride (NCl3) lewis structure?
NCl3 lewis structure contains three N-Cl bonds, nitrogen in the center position whereas all three chlorine atoms are at the terminal position. There is only one lone pair present on the central atom in the NCl3 lewis structure.
Let’s see how to draw its Lewis structure in a simple way-
Follow some steps for constructing the lewis dot structure of NCl3
1. Count total valence electron in NCl3
In the first step, we have to calculate how many valence electrons are available for NCl3. Because valence electron helps to know how many electrons are present in the outermost shell of an atom. So, for this just look at the periodic group of an atom to know its valence electron.
As nitrogen belongs to the 15th group and chlorine belongs to the 17th group in the periodic table. Hence valence electron for nitrogen is 5 and for chlorine, it is 7.
∴ Total valence electron available for drawing the leis structure of NCl3 = 5 + 7*3 = 26 electrons [∴NCl3 has three chlorine atoms and one nitrogen atom]
2. Find the least electronegative atom and placed it at center
Now it’s time to find the least electronegative atom in between nitrogen and chlorine for placing it at the center of lewis’s diagram. Because fewer electronegativity atoms share more electrons than a terminal atom.
So, the least electronegative atom in between nitrogen and chlorine is the nitrogen atom because electronegativity increase from left to right in the periodic table.
Therefore, place nitrogen at the center in the lewis diagram and chlorine spaced evenly around it.
3. Connect nitrogen and chlorine with a single bond
In this step, we have to connect each chlorine atom to the central atom(Nitrogen) with the help of a single bond.
Now look at the above structure and count how many valence electrons we used till now. As one single bond contains two electrons and we use three single bonds in the above structure. So, we used 6 electrons from the total of 26 valence electrons available for the NCl3 lewis structure.
∴ (26 – 6) = 20 valence electrons
Now we are left with 20 valence electrons more.
4. Placed remaining valence electrons starting from outer atom first
As we know, we always start placing electrons in the lewis diagram from the outer atom first. In this case, also we will place the remaining valence electron around the outer atom first(chlorine).
Chlorine needs 8 electrons to complete its octet but it has already 2 electrons because of a single bond. So, chlorine needs only 6 electrons around to complete its octet.
Therefore, Put 6 electrons around each chlorine atom in the structure.
As you see in the above structure, we placed 6 electrons around each chlorine atom. So, we used 24 electrons from the total of 26 valence electrons till now. And all chlorine atom in the above structure complete their octet as all have 8 electrons present around them.
But nitrogen central atom still needs 2 electrons to complete its octet or for maintaining stability.
5. Complete central atom octet and use covalent bond if necessary
Now we arrived at the final step for drawing the NCl3 lewis dot structure. In this step, we have to complete the central atom octet which is nitrogen in this case.
So, nitrogen needs 8 electrons around it to complete its octet but it has only 6 electrons around it(3 single bonds).
Therefore, put 2 electrons from the remaining valence electrons on nitrogen and complete its octet.
Lewis dot structure for NCl3
As you see in the above structure, each atom(nitrogen and chlorine) has completed its octet as each of them has 8 electrons around them.
So, this is the best and most stable Nitrogen trichloride lewis structure we have made.
What are the electron and molecular geometry of NCl3?
According to the VSEPR theory, the molecular geometry of NCl3 is trigonal pyramidal, and electron geometry is tetrahedral because nitrogen being pentavalent has Sp³ hybridization with 5 valence electrons in its outermost shell and it makes three bond pairs, one with each chlorine atom.
And one lone pair presents on a nitrogen atom that tries to repel the bonded pairs of electrons, as a result, electrons pairs move away from each other making its shape trigonal pyramidal.
Let’s see how to find the NCl3 molecular geometry step by step.
Follow three steps to find NCl3 molecular geometry
1. Find the Number of lone pairs present on the central atom of the NCl3 lewis structure
The presence of lone pair electrons very much affects the overall shape of the molecule. Therefore we need to find how many lone pairs are present in any lewis diagram to determine their geometry or shape.
The formula for finding lone pair in any lewis diagram-
∴ L.P = (V.E. – N.A.)/2
⇒ L.P. = Lone pair on the central atom
⇒ V.E. = valence electron of that central atom
⇒ N.A. = Number of atoms attached to that central atom
∴ According to the NCl3 lewis structure, nitrogen is the central atom that has 5 valence electrons and three atoms attached to it.
So, L.P. = (5 – 3)/2
= 1
Hence, the lone pair on the central atom of the NCl3 is 1.
2. Find hybridization number of NCl3
A hybridization number is basically a steric number that helps to know the hybridization of any molecule.
So, for finding the hybridization number of NCl3, use the formula given below-
∴ H = N.A. + L.P.
where H = hybridization number
N.A. = Number of atoms attached to the central atom
L.P. = lone pairs on that central atom
So, the central atom (nitrogen) is attached to 3 chlorine atoms and it has 1 lone pair.
So, H = 3 + 1
= 4
Hence the hybridization number is 4 which means NCl3 has Sp³ hybridization.
3. Use VSEPR theory or AXN method to determine NCl3 molecular geometry
According to Valence shell electron pair repulsion theory if the molecule contains Sp³ hybridization and 1 lone pair of electrons, then the shape of the molecule is trigonal pyramidal.
NCl3 molecular geometry or shape
You can use the AXN method also to determine the molecular shape or electron geometry of NCl3.
A represents the central atom.
X represents the bonded pairs of electrons to the central atom.
N represents the lone pairs of electrons on the central atom
As per the NCl3 lewis dot structure, nitrogen is the central atom that has 3 bonded pairs of electrons and one lone present on it.
Hence the formula of NCl3 becomes AX3N1
So, according to the VSEPR chart, if the molecule has the formula of AX3N1 then the molecule shape of that molecule is trigonal pyramidal, and electron geometry is tetrahedral.
Bonded atoms
Lone pair
Generic formula
Hybridization
Molecular geometry
Electron geometry
1
0
AX
S
Linear
Linear
2
0
AX2
Sp
Linear
Linear
1
1
AXN
Sp
Linear
Linear
3
0
AX3
Sp²
Trigonal planar
Trigonal planar
2
1
AX2N
Sp²
Bent
Trigonal planar
1
2
AXN2
Sp²
Linear
Trigonal planar
4
0
AX4
Sp³
Tetrahedral
Tetrahedral
3
1
AX3N1
Sp³
Trigonal pyramid
Tetrahedral
2
2
AX2N2
Sp³
Bent
Tetrahedral
1
3
AXN3
Sp³
Linear
Tetrahedral
3
2
AX3N2
Sp³d
T-shaped
Trigonal bipyramidal
The bond angle of NCl3 is 107.1° as it slightly decreases because of the lone pair present on nitrogen that creates repulsion between bond pairs and lone pair, hence causes to decrease in angle.
Nitrogen chloride polarity: is NCl3 polar or nonpolar
NCl3 is slightly polar because the lone pair present on the nitrogen generates repulsion between electrons makes the overall structure bent and this creates unequal charge distribution of charge within the structure that generates a permanent dipole moment.
Let’s understand it with the help of three factors. (a). Electronegativity (b). Dipole moment (c). Molecular shape
Three factors that indicate the polarity of NCl3
1. Electronegativity:
Electronegativity means the tendency of an atom to attracting electrons towards itself. If the electronegativity difference between the atoms is high then the polarity will also be higher. Now, look at the electronegativity of nitrogen and chlorine.
The difference between the electronegativity of nitrogen and chlorine is directly proportional to the Polarity of the NCl3 molecule.
The electronegativity of nitrogen is 3.04 and for chlorine, it is 3.16. And the difference of electronegativity between nitrogen and chlorine is 0.12 which is very little.
So, the N-Cl bond is non-polar due to less electronegativity difference among atoms but the overall molecule is polar due to the presence of lone pair on the central atom of the NCl3.
2. Dipole moment
Dipole moment ensures the strength of polarity between nitrogen and chlorine atom. As greater the dipole moment of the molecule, the more is the polar nature of that molecule. The net dipole moment of NCl3 is 0.6 D.
The dipole moment of NCl3 is very less but still, it is non-zero that causes NCl3 to become polar in nature.
In mathematical terms, dipole moment can be expressed as-
⇒ Dipole moment formula = charge on the atoms * the distance between them
∴ D = Q × R
3. Geometrical or molecular shape
The geometrical shape is also a big factor to determine is NCl3 polar or non-polar.
As we know the molecular shape of NCl3 is trigonal pyramidal which is asymmetric and when the shape of the molecule is asymmetric or distorted it doesn’t cancel the dipole moment across the molecule. Hence cause polar nature of the molecule
All these factors are enough to understand whether NCl3 is polar or non-polar.
⇒ We will calculate the formal charge on Nitrogen which is the central atom in the NCl3 dot structure.
⇒ Valence electron of nitrogen = 5
⇒ Non-bonding electrons = 2
⇒ Bonding electrons = 6
∴ 5 – 2 – 6/2
= 0 is the formal charge on the central atom in Nitrogen trichloride lewis structure.
FAQ
How many bond pairs and lone pairs a central atom has in the NCl3 lewis dot structure?
As per the NCl3 lewis structure, nitrogen is the central atom that has only one lone pair on it and three bond pair which is attached to chlorine atoms in the structure.
Why does NCl3 have a greater bond angle than NH3?
As chlorine is bigger than hydrogen in terms of size and electronegative. Being more electronegativity of chlorine helps to attract electrons towards itself and due to internal repulsion between chlorine-chlorine ions, NCl3 bond angle increase.
More electronegative atoms cause more repulsion. Due to this the lone pair-lone pair repulsion is higher in NCl3 than NH3 that ultimately making its bond angle higher.
∴ l.p.-l.p. > l.p-b.p >b.p-b.p.
Why NCl3 molecular geometry is the trigonal pyramid and its electron geometry is tetrahedral?
Always remember, molecular geometry only considers bond pairs of electrons to determine the shape of any molecule, and electron geometry considers both bond pair and lone pair to determine the geometry of any molecule.
As NCl3 contains one lone pair and three bonded pairs. So, according to the VSEPR chart, the electron geometry of NCl3 is tetrahedral while molecular geometry is trigonal pyramidal.
Is the lewis structure of NCl3 the same as NF3 and NH3?
Yes, the Nitrogen trichloride lewis structure is almost the same as NF3 and NH3.
NF3 lewis structure has 3 fluorine and 1 nitrogen atom connected with three single bonds and NH3 lewis structure has 3 hydrogens and 1 nitrogen connected with three single bonds also.
In all these molecules(NH3, NF3, and NCl3), there is one lone pair present on the central atom.
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
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