Drawing the Lewis Structure for PF5

Viewing Notes:

  • PF5 is similar to PCl5 and PBr5. If you can do those Lewis structures PF3 will be easy.
  • In the PF5 Lewis structure Phosphorus (P) is the least electronegative so it goes in the center.
  • In the Lewis structure for PF5 there are a total of 40 valence electrons. Five pairs will be used in the chemical bonds between the P and F.

Transcript: 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.