Draw the Lewis structure for NH3.
When I draw a Lewis structure, the first thing I need to do is count the number
of valence electrons in that particular molecule.
So, here I have nitrogen, which has five electrons in the valence shell, and
I have hydrogen, each has one valence electrons, and there are three of them.
So that gives me a total of three electrons from hydrogen and
five from the nitrogen, so I have a total eight electrons.
Now, I'm going to draw my nitrogen as my central atom,
because hydrogen must always be a terminal atom.
And I'm going to draw the skeletal structure all with single bonds.
At this point I've used six electrons, so I have two remaining.
Note that the hydrogens don't want any more electrons.
They only want a duet of electrons, so
I don't need to add any electrons to my terminal atoms.
So those last two electrons can be added to nitrogen.
When I look at each of these atoms.
So if I look at my hydrogen it has two electrons, two electrons,
two electrons, which it, makes it happy.
And when I look at my nitrogen, it has eight electrons around it.
So my nitrogen has its octet.
I don't need to look at forming double bonds or
anything else, or rearranging electrons or connectivities of atoms, because all of
my atoms either have their duet for hydrogen or the octet, which nitrogen has.