Coordination Compounds

Let the oxidation state of Iron (Fe) be .
The cyanide ligand (CN) has a charge of -1. There are 6 cyanide ions.
The overall charge on the complex ion is -3.
The equation for the sum of oxidation states is: .
.
Therefore, the oxidation state of Fe is +3.

1. Dissociation: Double salts (e.g., Mohr's salt) completely dissociate into their constituent simple ions when dissolved in water. Coordination compounds (e.g., Potassium ferrocyanide) do not completely dissociate; the complex ion remains intact.
2. Properties: The properties of a double salt are essentially the same as those of its constituent compounds. The properties of a coordination compound are different from its constituents.
3. Valency: In double salts, the metal exhibits normal valency. In coordination compounds, the metal satisfies two types of valencies: primary (oxidation state) and secondary (coordination number).

Definition: A monodentate (or unidentate) ligand is a ligand that has only one donor atom capable of forming a coordinate bond with the central metal ion.
Examples:
1. Ammonia (:NH ) - The Nitrogen atom is the donor.
2. Water (H O:) - The Oxygen atom is the donor.
3. Chloride ion (Cl ) - Acts as a donor.