Question

Write the formula for a complex formed between Ni 2+ and NH3, with a coordination number of 5.


Write the formula for a complex formed between Ni 2+ and CN–, with a coordination number of 4.

I am having trouble with these problem because I don't really understand what coordination numbers are. I know that Ni is 2+ and I believe that NH3 is 1-, but I don't understand how to make the coordination number 5.

Thank you so much.

Answers

DrBob222
Coordination number has slightly different meanings depending upon how it is used. One is in crystallography and the other is in complex formation. Here is a site that you can read about both.
http://en.wikipedia.org/wiki/Coordination_number

Basically, coordination number in complex ion formation is the number of atoms bound to the central atom. So if you want Ni^2+ and CN^- with coordination number of 4 you write [Ni(CN)4]^2- . The 2- charge is figures just like oxidation numbers; i.e., Ni ion is ^2+ and 4 CN ions at -1 each is -4. Then +2 + (-4) = -2.
You're right that Ni^2+ is 2+ but NH3 is zero. All compounds are neutral; Ni is 2+ because that's the charge on the ion.
Kim
Rearrange this equation to isolate a
b
(a+ c) (d-e)=f
R
What is the formula of the compound formed between the ions CO32- and Ni2+

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