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This is the PF6- Lewis structure. Phosphorus has 5 valence electrons; Fluorine has 7. We
have 6 Fluorines, and we need to add in this valence electron up here for a total of 48
valence electrons. Phosphorus is the least electronegative. We'll put that at the center
and then we'll put the 6 Fluorines around the outside. We'll form chemical bonds between
the Fluorine and the Phosphorus. Each of these is 2 valence electrons. So we have six bonds.
We've used 12 valence electrons. Completing the octets of the Fluorines, we have 12, 14,
16, and 48. So we've used all 48 valence electrons in the PF6- Lewis structure. The key here
is that Phosphorus is below Period 2 in the periodic table. That means it can have an
expanded octet. It can hold more than 8 valence electrons. Here, it's holding 2, 4, 6, 8,
10, 12. That's OK, though. Because of that expanded octet, we can do that. If you were
to look at the formal charges, you would find that Phosphorus has a formal charge of -1.
That makes sense, because this is negative up here. So that's the Lewis structure for
PF6-. This is Dr. B., and thanks for watching.