Let's do the N2H4 Lewis structure. Nitrogen has
five valence electrons. We have two Nitrogens. Plus, Hydrogen has one valence electron and we have
four of them.
So 10 + 4: we have a total of
14 valence electrons.
Put the Nitrogens in the center
because the Hydrogens always go on the outside.
We have
4 Hydrogens. We'll put 2
on each Nitrogen, like this.
Then we'll put two valence electrons between the atoms to form chemical bonds. We've used six, eight, ten ...
back in the center,
twelve, and fourteen.
So let's check our octets now that we've
used all of the 14 valence electrons
we started with.
All of the Hydrogens have two valence 
electrons. Hydrogen only needs two for a
full outer shell, so all of our Hydrogens
are OK.
The Nitrogens
have eight valence electrons,
so their outer shells are full.
So we've used all 14 valence electrons,
we've satisfied the outer shells, they're
all full for each of the elements
and that's it.
That's the N2H4 Lewis structure.
This is Dr. B.,
and thanks for watching.
