Chemistry class 12th Important_Terms_Coordination_Compounds

Important Terms in Coordination Compounds


### 1. Coordination Entity
A coordination entity consists of a central metal atom or ion surrounded by ligands. Example:
[Co(NH3)6]3+.


### 2. Central Metal Atom/Ion
The metal atom or ion in a coordination compound that binds to ligands. Example: Fe in
[Fe(CN)6]4-.


### 3. Ligands
Molecules or ions that donate a pair of electrons to the central metal.
- **Monodentate**: Bind through one donor atom (e.g., Cl-, NH3).
- **Bidentate**: Bind through two donor atoms (e.g., ethylenediamine).
- **Polydentate**: Bind through multiple donor atoms (e.g., EDTA).


### 4. Coordination Number
The number of ligand donor atoms attached to the central metal. Example: In [Cr(NH3)6]3+, Cr has
a coordination number of 6.


### 5. Oxidation State
The charge on the central metal after removing ligands and counting electrons. Example: In
[Fe(CN)6]4-, Fe has an oxidation state of +2.


### 6. Coordination Sphere
The metal ion and its directly attached ligands are enclosed in square brackets. Example:
[Cu(NH3)4]SO4 (only [Cu(NH3)4]2+ is the coordination sphere).


### 7. Chelation
When a polydentate ligand forms a ring structure with a metal ion, increasing stability. Example:
EDTA forms strong chelates with metals.


### 8. Isomerism in Coordination Compounds