Chemical Bonding: Br₃^- Lewis Structure

Drawing the Lewis Structure for Br₃^-

Viewing Notes:

• The Br₃^- Lewis structure has a total of 22 valence electrons. Each Bromine (Br) atom contributes 4 valence electrons and the negative sign (-) provides an additional valence electron for a total of 22.
• Be sure to put brackets and a - (negative sign) around the dot structure to show that Br₃^- is an ion with negative one charge.

Transcript: This is the Br3- Lewis structure. Bromine is in group 7 or 17, so it has 7 valence electrons. We have 3 Bromines, and then we need to add in this negative up here, an additional valence electron, for a total of 22 valence electrons for the Br3- Lewis structure. We have three Bromines.

We'll line them up like this, and then we'll take the electrons--we have 22--and we'll place two electrons between atoms to form chemical bonds. Then we'll go around the outside atoms to fill their octets. We have 2, 4, 6, 8, 16, and then back to the central Bromine, 18 and 20. So everything has octets now, but we've only used 20. We have an additional 2 valence electrons that we're going to have to do something with.

Because Bromine is below period 2 in the periodic table, that means it can have an expanded octet. It can have more than 8 valence electrons. So we'll put these last two valence electrons on the central Bromine. So we've now used all 22 valence electrons. We have octets on the outer Bromines. The inner Bromine has 10 valence electrons, but that's OK because Bromine can have an expanded octet. The last thing we need to do for the Br3- Lewis structure is put brackets around it to show that we have a negative ion.

And there you have it: the Lewis structure for Br3-. This is Dr. B., and thanks for watching.