N2H2 (diimide) has two nitrogen atoms and two hydrogen atoms. In the lewis structure of N2H2, there is a double bond between the two nitrogen atoms, and each nitrogen is attached with one hydrogen atom, and on each nitrogen atom, there is one lone pair.
Here’s how you can draw the N2H2 lewis structure step by step.
Step #1: draw sketch
Step #2: mark lone pairs
Step #3: mark charges
Step #4: minimize charges
Step #5: minimize charges again (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 and hydrogen has one valence electron.
Since N2H2 has two nitrogen atoms and two hydrogen atoms, so…
Valence electrons of two nitrogen atoms = 5 × 2 = 10
Valence electrons of two hydrogen atoms = 1 × 2 = 2
And the total valence electrons = 10 + 2 = 12
- Second, find the total electron pairs
We have a total of 12 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 = 12 ÷ 2 = 6
- 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 there are only two atoms remaining and both atoms are nitrogen, so we can assume any one as the central atom.
Let’s assume that the central atom is right nitrogen.
Therefore, place nitrogens in the center and hydrogens on either side.
- And finally, draw the rough sketch
#2 Mark Lone Pairs
Here, we have a total of 6 electron pairs. And three bonds are already marked. So we have to only mark the remaining three 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. And hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell.
Always start to mark the lone pairs from outside atoms. Here, the outside atoms are hydrogens and left nitrogen. But no need to mark on hydrogen, because each hydrogen has already two electrons.
So for left nitrogen, there are two lone pairs, and for right 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 left nitrogen atom, formal charge = 5 – 4 – ½ (4) = -1
For right nitrogen atom, formal charge = 5 – 2 – ½ (4) = +1
For each hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0
Here, both nitrogen atoms have charges, so mark them on the sketch as follows:
The above structure is not a stable lewis structure because both nitrogen atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.
#4 Minimize Charges
Convert a lone pair of the left nitrogen atom to make a new N — N bond with the right nitrogen atom as follows:
In the above structure, you can see that the central atom (right nitrogen) forms an octet. Hence, the octet rule is satisfied.
Also, the above structure is more stable than the previous structures. Therefore, this structure is the stable lewis structure of N2H2.
Next: CH3Cl Lewis Structure