## Finding Coordination Number and Oxidation State [ENDORSED]

Julia_Gordon_2A
Posts: 30
Joined: Wed Sep 21, 2016 2:57 pm

### Finding Coordination Number and Oxidation State

I am slightly confused on how to find the coordination number and oxidation state for complex ions. Could someone please explain how to find both of those values for
[Pt(CN)(NH3)3]+ ?

Thank you!

Helena Vervaet 1N
Posts: 26
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Finding Coordination Number and Oxidation State

The coordination number essentially means the number of bonds that form around the central atom (The transition metal). In the example you gave, the coordination number would be 4 because there are 4 molecules that form bonds with Pt. In order to find the oxidation number, you need to look at the charge of each piece of the complex. We know that each NH3 has a +1 charge so there are three NH3's for a combined total of +3. CN has a -1 charge. Since the overall complex has a +1 charge, Pt has to have a -1 oxidation state because (+3) + (-1) + (-1) = +1.

Julia_Gordon_2A
Posts: 30
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Finding Coordination Number and Oxidation State

It says the oxidation state for that complex ion is +2. And wouldn't NH3 have a neutral charge?

Matt_Coopersmith_4H
Posts: 20
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Finding Coordination Number and Oxidation State  [ENDORSED]

Hi Julia! You are absolutely right. With the equation, [Pt(CN)(NH3)3]+ , the overall charge of the coordination compound is a 1+ charge. In order to find the oxidation state, you have to look at each individual component of the compound as suggested by Helena. To break it up, it would look like this:

Cyano is actually CN- and is thus CN = 1-
Ammine is NH3 and has a charge of 0.

Therefore, the charge inside the brackets would simply be [-1]. In order to make the entire coordination a [+] compound, you must find the charge of Platinum that will work. Therefore, the Pt must have a charge of 2+, making the oxidation number 2.

Hope this helps!

Helena Vervaet 1N
Posts: 26
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Finding Coordination Number and Oxidation State

Thank you for correcting my mistake, Matt! I keep confusing NH3 with NH4, which is why I thought there was a +1 charge. Sorry if I caused any confusion!

Cobie_Allen_1H
Posts: 24
Joined: Wed Sep 21, 2016 2:56 pm

### Re: Finding Coordination Number and Oxidation State

Julia_Gordon4I wrote:I am slightly confused on how to find the coordination number and oxidation state for complex ions. Could someone please explain how to find both of those values for
[Pt(CN)(NH3)3]+ ?

Thank you!

Yes, this confuses me a lot! Any help would be great!

Raul Hernandez
Posts: 28
Joined: Fri Jun 17, 2016 11:28 am

### Re: Finding Coordination Number and Oxidation State

I have another question regarding the coordination number: if one of the molecules attached to the central metal is bidentate, would we count that as another bond?
For example, if there's a central metal with 4 ligands and 1 of those ligands happens to be bidentate, would the coordination number be 4 or 5, then?

Khachik_Hmayakyan_2E
Posts: 25
Joined: Sat Jul 09, 2016 3:00 am

### Re: Finding Coordination Number and Oxidation State

Yes. Polydentate ligands can bond to the transition metal at more than one site, therefor a bidentate ligand has two areas on it which can bond to the central transition metal atom. This allows bidentate ligands to be considered as 2 coordination numbers when counting the total number of bonds.