Determine Coordination Number of Metal Ions

[Teemo]

Is there any way (ex. MO theory, valence electrons, etc) to determine the coordination number of a metal ion with another ion? I know it is generally a multiple of the oxidation number of the metal ion. However, for something like Ni and NH₃. how would I know that it's a coordination number of 6?

 

[mooncrater]

I would have suggested you the EAN method . But it has exceptions (thats what I think.).So I think you'll have to mug them up.Well, you will remember them through practise .