Give reason for the fact that amongst `Ni(CO)_(4)[Ni(CN)_(4)]^(2-)` and `NiCI_(4)^(2-), Ni(CO)_(4)` and `[Ni(CN)_(4)]^(2-)` are diamagnetic whereas `[NiCI_(4)]^(2)` is paramagnetic are diamagnetic whereas` [NiCI_(4)]^(2)` is paramagnetic .

Explanation

To determine why `Ni(CO)4` and `[Ni(CN)4]^(2-)` are diamagnetic while `[NiCl4]^(2-)` is paramagnetic, we need to analyze the electronic configuration of nickel in these coordination compounds and how the ligands affect the d-orbitals through crystal field splitting.

### Step-by-Step Solution:

1. **Identify the oxidation state of Nickel**:
- In all three complexes, nickel is in the +2 oxidation state. The electronic configuration of Ni in its elemental form is `[Ar] 3d^8 4s^2`. When it loses two electrons to form Ni²⁺, the configuration becomes `[Ar] 3d^8`.

2. **Determine the nature of the ligands**:
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