This is Dr. B. Let's do the PF3 Lewis structure.
On the periodic table: Phosphorus, 5 valence
electrons; plus Fluorine, we have 7, but we
have three Fluorines so we...5 plus 21: 26
total valence electrons.
We'll put the P at the center, and we've got
three F's.
Let's put them like this.
We'll start by putting electrons between each
atom, two of them, to form a chemical bond.
And then around the outside atoms.
So we've used 2, 4, 6, so we have a total
of 20 to use up the 26.
So 2, 4, 6, 8, 10, 12, 24, and we have two
left, and we'll put those on the central atom.
At this point, everything has eight valence
electrons.
So we've used 26 valence electrons that we
started with.
Everything has an octet.
If we wanted, we could check the formal charges
and you'd see that those work out.
So this is the best structure for PF3.
This is Dr. B., and thanks for watching.
