`[CoF_6]^(3-)` is a coordination complex ion.
What is the oxidation number of cobalt in the complex ?

Explanation

To determine the oxidation number of cobalt in the coordination complex ion \([CoF_6]^{3-}\), we can follow these steps:

### Step 1: Identify the charge of the complex ion
The overall charge of the complex ion \([CoF_6]^{3-}\) is given as \(-3\).

### Step 2: Identify the charge of the ligands
In this complex, the ligand is fluoride ion (\(F^-\)). Each fluoride ion has a charge of \(-1\). Since there are 6 fluoride ions, the total charge contributed by the ligands is:
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