Drawing the Lewis Structure for PBr3

Viewing Notes:

  • PBr3 is similar to PCl3 and PF3. If you can do those Lewis structures PBr3 will be easy.
  • In the PBr3 Lewis structure Phosphorus (P) is the least electronegative so it goes in the center.
  • In the Lewis structure for PBr3 there are a total of 26 valence electrons. Three pairs will be used in the chemical bonds between the P and Br.

Transcript: Hi, this is Dr. B. Let's do the PBr3 Lewis structure. On the periodic table, Phosphorus in group 5 has 5 valence electrons. Bromine, group 7 or 17, has 7 valence electrons, and then we have three Bromines so we have to multiply it by three. Five plus seven times three, so 5 plus 21 is 26 valence electrons. Put the Phosphorus right here, and then we have three Bromines, so we'll put those like this.

We'll put a pair of electrons between each Phosphorus and Bromine to form a chemical bond. We've used six valence electrons; we have 26 total. Let's put them on the Bromines, try to get octets there. So we have 6, 8, 10, 24, and we have (26 minus 24), we have two left over. We'll just put them right here on the central Phosphorus atom. At this point, everything has eight valence electrons. The Bromines, they're all the same, they have eight; and the Phosphorus in the center, it has eight.

So we've filled the octets for everything. We've used 26 valence electrons. We're pretty much done with this Lewis structure for PBr3. If you wanted to check, you could look at the formal charges and make sure everything's OK. If you did that, you'd find that they're all zero.

So this is the best structure for PBr3, and this is Dr. B., and thanks for watching.