### Drawing the Lewis Structure for PBr5

Viewing Notes:

• PBr5 is similar to PCl5 and PF5. If you can do those Lewis structures PBr3 will be easy.
• In the PBr5 Lewis structure Phosphorus (P) is the least electronegative so it goes in the center.
• In the Lewis structure for PBr5 there are a total of 40 valence electrons. Five pairs will be used in the chemical bonds between the P and Br.

Transcript: Hi, this is Dr. B. Let's do the Lewis structure for PBr5. Phosphorus has 5 valence electrons, plus 7 for Bromine, but we have five Bromines. We have 5, plus 7 times 5, is 35 so we have 40 total valence electrons. Put the Phosphorus in the center and then the Br's go on the outside, like so. We'll draw a line between each Phosphorus and Bromine to represent a chemical bond, and that's going to be two valence electrons. So we've used 2, 4, 6, 8, 10 valence electrons. We have 30 left. So let's put them on the outer atoms to form octets for the Bromines. So we have 10, 12, 14, and 40.

So all the Bromines right now have eight valence electrons, 2, 4, 6, 8; so their outer shells are full. And the Phosphorus has 2, 4, 6, 8, 10 valence electrons, but that's going to be OK. It's in period 3, or row 3 of the periodic table, so it can have more than eight valence electrons. We've used up all our valence electrons, all 40 here. We've got octets on these, and the Phosphorus, that's OK.

We could check the formal charges if we wanted to make sure that this was the best structure. We'd find that they're all zero, so that's going to be good, too.

And that's the PBr5 Lewis structure. This is Dr. B., and thanks for watching.

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