Naming Coordination Number Textbook Problem

[Danielle DIS2L]

I am a bit confused with b and c

how come for b Cl does not have a subscript of 3 which is the oxidation state of cobalt whereas for c, Br has a subscript of 3 when the oxidation state of cobalt is 3

[Selena Quispe 2I]

So Cl does not have a subscript of three because the sulfato has a charge of -2 and the chlorine has a charge of -1 making it have an overall charge of -3 but the oxidation state of Cobalt (+3) cancels the charges out. For part c NH3 does not have a charge and neither does water so the bromine has to be three because it has a -1 charge so it can cancel charges with the (+3) in Cobalt. I hope this helps and good luck studying!

[SophiaBarden 2E]

When we have ions bonded to a bracketed [] compound, the we take the charge of the full compound into consideration, not just the charge of the metal. For b, c calculate the charge of the compound (sulfato with a 2- and Cobalt with a 3+) which is an overall charge of +1, and we add subsequent Chlorine ions for a neutral charge of 0; which in this case, we only need 1 Chlorine.

[Irene Nguyen 2J]

Hi! The charge for the ion in the brackets is +1 (for +3 in Cobalt and -2 in SO4), so for the entire thing to be neutral, you need only one Cl to get an overall charge of 0. In part c, the charge of the ion is +3 as NH3 and H2O are neutral ligands and Cobalt (III) has a charge of +3. To have an overall charge of 0, there needs to be three Br as each Br is -1. Hope this helps!