NCl3 (Nitrogen trichloride) Lewis Structure

There are 3 chlorine atoms and one nitrogen atom in NCl3. Nitrogen trichloride (NCl3) lewis structure contains three N-Cl bonds. There are one lone pair on nitrogen atom and three lone pairs on each chlorine atom. Lewis structure of NCl3 can be drawn by using valence electrons of nitrogen and chlorine atoms. Also, there are no charges on atoms in NCl3. Steps of drawing the lewis structure of NCl3 are explained in detail in this tutorial.



Lewis structure of NCl3

NCl3 (Nitrogen trichloride) lewis structure

There are three sigma bonds and one lone pair around nitrogen atom which is the center atom in NCl3.


Steps of drawing the lewis structure of NCl3

There are few steps to draw a lewis structure of a molecule or ion. Because NCl3 is a simple molecule, those all steps are not used to draw it. But, you can learn good basic things from this example.

  1. Find total number of electrons of the valance shells of chlorine atoms and nitrogen atom
  2. Total electrons pairs as lone pairs and bonds
  3. Center atom selection
  4. Mark lone pairs on atoms
  5. Mark charges on atoms if there are charges on atoms.
  6. Check the stability and minimize charges on atoms by converting lone pairs to bonds to obtain best lewis structure.

Total number of electrons of the valance shells of NCl3

There are two elements in NCl3 molecule; chlorine and nitrogen. Chlorine is a group VIIA element and has seven electrons in its last shell (valence shell). Nitrogen is a group VA element in the periodic table and contains five electrons in its last shell. Now, we know how many electrons includes in valence shells of chlorine and nitrogen atoms.


To find out total valence electrons given by a particular element, you should multiply number of electrons of the valance shell by the number of atoms of that element in respective molecule.


  • valence electrons given by chlorine atoms = 7 * 3 = 21
  • valence electrons given by nitrogen atom = 5*1 = 5

  • Total valence electrons = 21 + 5 = 26

Total valence electrons pairs

Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells

Total electron pairs are determined by dividing the number total valence electrons by two. For, NCl3, Total pairs of electrons are 13.




Center atom of NCl3 molecule

To be the center atom, ability of having greater valance and being most electropositive element in the molecule are important facts. These are not essential. But those two facts play a major role in selecting center atom of a molecule.

  1. Maximum valence: Nitrogen's maximum valence is 5. Chlorine's maximum valence is 1. From that fact, chlorine has the high priority to be the center atom.
  2. Most electropositive element: Nitrogen's electronegativity is slightly above than chlorine's electronegativity. Therefore, chlorine is more electropositive than nitrogen. In this occasion too, chlorine has the highest chance to be the center atom.
  3. But, in this NCl3, nitrogen is the center atom though above 1 and 2 facts tells chlorine is the center atom. This happens because nitrogen should have at least three bonds get it's octal. Otherwise, nitrogen cannot become stable.
NCl3 basic skech structure

Lone pairs on atoms

Now, we knew the center atom and basic sketch of NCl3 molecule. As the next step, we can start to mark lone pairs on atoms. Remember that, there are total of 13 electron pairs as bonds and lone pairs.

  • There are already 3 N-Cl bonds in the above drawn sketch. Now only 10 (13-3) electron pairs remains to mark on atoms.
  • Usually, those remaining electron pairs should be started to mark on outside atoms (in this case, on chlorine atoms). So, we can mark lone pairs on chlorine atoms. Each chlorine atom will take 3 lone pairs and total of 9 electron pairs are marked on all 3 chlorine atoms.
  • Now, only 1 lone pair is remaining and it is marked on nitrogen atom.
mark lone pairs on nitrogen and chlorine atoms in NCl3

Mark charges on atoms and check the stability and minimize charges on atoms by converting lone pairs to bonds

According to the above structure, there are no charges on nitrogen and chlorine atoms. Therefore, we don't need to doing the step of reducing charges to get the most stable structure. That means, we have already got the lewis structure of NCl3 molecule.




Questions


how many total valence electrons are in NCl3?

As explained earlier, nitrogen has five electrons in its last shell. Chlorine has seven electrons in its valence shell. Because, there are three chlorine atoms, they give 21 electrons. So, there are 26 total valence electrons in NCl3.



What are the similar lewis structures to nitrogen trichloride lewis structure?

  • NF3 - Similar from number of lone pairs on outside atoms and number of bonds around center atom.




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