Question

What is the metal oxidation state in `Ni(CO)_4`?

Answer 1

We have zerovalent nickel, i.e. `Ni^(0)`

Explanation:

`"Oxidation number"` is the charge left on the central atom when all the bonding pairs of electrons are removed, with the charge devolved to the most electronegative atom.

For `Ni(CO)_4`, we break the `Ni-CO` bond and we get `Ni^0` `+4xx""^(-):C-=O^+`. And thus nickel has a formal oxidation state of `"ZERO".`

Because `Ni(CO)_4` is quite volatile, its formation forms the basis for the Mond process for nickel purification.