(a) What is a ligand ? Give an example of a bidentate ligand.
(b) Explain as to how the two complexes of nickel, `[Ni(CN)_(4)]^(2-)` and `Ni(CO)_(4)` have different structures but do not differ in their magnetic behaviour. (Ni = 28)

Explanation

(a) Ligands - The ions or molecules bound to the central atom / ion in the coordination entity are called ligands.
Example of a bidenate ligand : `H_(2)N CH_(2)CH_(2)NH_(2)` (ethylenediamine)
(b) `[Ni(CN)_(4)]^(2-)` is a square planar complex which is diamagnetic as no unpaired electron is present.
`[Ni(CO)_(4)]` is a tetrahedral complex which is diamagnetic due to absence of unpaired electrons.