NH2Cl (monochloramine) has one nitrogen atom, two hydrogen atoms, and one chlorine atom. In the lewis structure of NH2Cl, there are three single bonds around the nitrogen atom, with two hydrogen atoms and one chlorine atom attached to it. The nitrogen atom has one lone pair, and the chlorine atom has three lone pairs.
Here’s how you can draw the NH2Cl lewis structure step by step.
Step #1: draw sketch
Step #2: mark lone pairs
Step #3: mark charges (if there are)
Let’s break down each step in detail.
#1 Draw Sketch
- First, determine the total number of valence electrons
Hence, nitrogen has five valence electrons, hydrogen has one valence electron, and chlorine has seven valence electrons.
Since NH2Cl has one nitrogen atom, two hydrogen atoms, and one chlorine atom, so…
Valence electrons of one nitrogen atom = 5 × 1 = 5
Valence electrons of two hydrogen atoms = 1 × 2 = 2
Valence electrons of one chlorine atom = 7 × 1 = 7
And the total valence electrons = 5 + 2 + 7 = 14
- Second, find the total electron pairs
We have a total of 14 valence electrons. And when we divide this value by two, we get the value of total electron pairs.
Total electron pairs = total valence electrons ÷ 2
So the total electron pairs = 14 ÷ 2 = 7
- Third, determine the central atom
Here hydrogen can not be 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.
Now we have to choose the central atom from nitrogen and chlorine. Place the least electronegative atom at the center.
Since nitrogen is less electronegative than chlorine, assume that the central atom is nitrogen.
Therefore, place nitrogen in the center and hydrogen and chlorine on either side.
- And finally, draw the rough sketch
#2 Mark Lone Pairs
Here, we have a total of 7 electron pairs. And three bonds are already marked. So we have to only mark the remaining four electron pairs as lone pairs on the sketch.
Also remember that nitrogen is a period 2 element, so it can not keep more than 8 electrons in its last shell. Hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell. And chlorine is a period 3 element, so it can keep more than 8 electrons in its last shell.
Always start to mark the lone pairs from outside atoms. Here, the outside atoms are hydrogens and chlorine. But no need to mark on hydrogen, because each hydrogen has already two electrons.
So for chlorine, there are three lone pairs, and for nitrogen, there is one lone pair.
Mark the lone pairs on the sketch as follows:
#3 Mark Charges
Use the following formula to calculate the formal charges on atoms:
Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons
For nitrogen atom, formal charge = 5 – 2 – ½ (6) = 0
For each hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0
For chlorine atom, formal charge = 7 – 6 – ½ (2) = 0
Here, the atoms do not have charges, so no need to mark the charges.
And in the above structure, you can see that the central atom (nitrogen) forms an octet. Hence, the octet rule is satisfied.
Therefore, this structure is the stable lewis structure of NH2Cl.
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