Nitrogen trichloride (NCl3) lewis dot structure, molecular geometry, polar or non-polar, hybridization

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NCl3 lewis structure molecular geometry

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.
  • It is a very explosive substance.
  • It has a molar mass of 120.36 g/mol.
Name of MoleculeNitrogen trichloride
Chemical formulaNCl3
Molecular geometry of NCl3Trigonal pyramid
Electron geometry of NCl3Tetrahedral
HybridizationSp³
Bond angle107.1º
Total Valence electron for NCl326
The formal charge of NCl30

How to draw Nitrogen trichloride (NCl3) lewis structure?

Lewis diagram is a representation of how electrons are arranged around individual atoms in a structure. NCl3 lewis structure is the same as the NF3 structure. It contains one nitrogen atom at the center and three chlorine atoms spaced evenly around it.

One lone pair is present on the central atom of the NCl3 lewis dot structure and three lone pairs on each chlorine atom.

Let’s see how to draw this 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 in Nitrogen = 5

⇒ Total valence electron in Chlorine = 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]

Valence electron present in nitrogen trichloride (NCl3) lewis structure

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.

central atom in NCl3 lewis structure

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.

Connect chlorine to nitrogen with 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.

Place remaining valence electron in NCl3

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.

Nitrogen trichloride (NCl3) lewis structure

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 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.

Nitrogen trichloride NCl3 molecular geometry or shape

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 atomsLone pairGeneric formulaHybridizationMolecular geometryElectron geometry
10AXSLinearLinear
20AX2SpLinearLinear
11AXNSpLinearLinear
30AX3Sp²Trigonal planarTrigonal planar
21AX2NSp²BentTrigonal planar
12AXN2Sp²LinearTrigonal planar
40AX4Sp³TetrahedralTetrahedral
31AX3N1Sp³Trigonal pyramidTetrahedral
22AX2N2Sp³BentTetrahedral
13AXN3Sp³LinearTetrahedral
32AX3N2Sp³dT-shapedTrigonal 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.

NCl3 molecular geometry bond 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.

What is the formal charge in NCl3 lewis dot structure and how to calculate it?

The formal charge shows that which atom(Nitrogen or Chlorine) has more positive or negative charge present on it.

As we know any lewis diagram can be most stable when the formal charges on the atom are lowest or zero.

To calculate the formal charge in NCl3 lewis structure. Use this equation:

⇒ Formal charge = (Valence electrons – unbonded electrons – 1/2 bonded electrons)

⇒ 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 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 makes 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 determining 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.

Summary

Now it’s time to take a quick review of an overall article with the help of some bulleted points.

  • The total valence electron available for the Nitrogen trichloride lewis structure is 26.
  • The hybridization of NCl3 is Sp³.
  • Nitrogen trichloride is slightly polar in nature.
  • The molecular geometry of NCl3 is trigonal pyramidal and its electron geometry is tetrahedral.
  • NCl3 lewis dot structure contains 1 lone pair and 3 bonded pairs. 
  • The net dipole moment of Nitrogen trichloride is 0.6 D.
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