Hi, this is Dr. B. Let's do the Lewis structure
for PF5.
On the periodic table, Phosphorus is in group
5, it has 5 valence electrons.
Fluorine, group 7, but we have five of those,
so we need to multiply that 7 by 5.
Five plus 35: 40 valence electrons.
We'll put the Phosphorus in the center, and
then the Fluorines, we have five of them,
let's put them around it like this.
We'll connect the Phosphorus to each Fluorine
with a single line representing a pair of
electrons, like that.
So we've used 2, 4, 6, 8, 10 valence electrons.
That means we have 30 left.
And then we'll fill the octets for the outer
atoms.
We have 30 valence electrons.
Two, 4, and 40.
At this point, all the Fluorines have 8 valence
electrons, so their outer shells are full.
The Phosphorus in the center has 10 valence
electrons, but that's OK.
Phosphorus is in period 3 of the periodic
table, and those elements and the ones below
can hold more than eight valence electrons.
If you wanted to make sure you had the right
structure, you could check the formal charges
and you'd see that they're all zero.
So this is the correct structure for PF5.
This is Dr. B., and thanks for watching.
