Charge of the metal

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Vera Khurshudyan 1K
Posts: 12
Joined: Fri Sep 26, 2014 2:02 pm

Charge of the metal

Postby Vera Khurshudyan 1K » Wed Nov 19, 2014 5:40 pm

How do we determine the charge of the metal for example cobaltate (III) in K3[CoF6]. How do you know it is 3?

HimaniMadnawat3L
Posts: 15
Joined: Fri Sep 26, 2014 2:02 pm

Re: Charge of the metal

Postby HimaniMadnawat3L » Wed Nov 19, 2014 7:36 pm

In this compound, we know that [CoF6] is 3- itself since the K has a +1 charge. This is similar to a compound like AlCl3 where the +3 charge on the aluminum crosses over to become a subscript of the chlorine and the -1 charge of the chlorine crosses and becomes a subscript of the Aluminum. So, the [CoF6] has a total charge of 3-, and we know that fluorine's charge is -1 since the oxidation number of halogens is usually -1. There are 6 fluorines which gives us a 6- charge, but the total charge of the anion ([CoF6]3-) is 3-. So, to bring the charge up to 3-, Co must have a 3+ charge to balance with the 6- charge from the fluorine. Hope that was helpful.

martha-1I
Posts: 76
Joined: Fri Sep 26, 2014 2:02 pm

Re: Charge of the metal

Postby martha-1I » Sun Nov 23, 2014 2:33 pm

Since K3[CoF6] does not indicate a charge, we know that the metal must cancel out any of the charges that the other elements have in order to give us a total charge of zero. In this example the total charge, excluding the metal Co, is +3 (for K) -6 (for F). These add up to a -3 charge. Since the whole compound has no charge that means that Co must have a +3 charge in order to cancel out the -3 charge from K and F.


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