Question

What is the significance of 3+ in [Co(CN)₆]³⁺ ? How does it affect the oxidation state of Cobalt ?

Answer 1

I think it should be 3- instead of 3+. It denotes the net charge on the complex. The charge in single CN- is -1. SO, total negative charge due to CN is -6 and the total charge on the complex is 3+. So, the oxidation state of Co is 3+. This is how the net charge decides the oxidation of Cobalt.