6. Coordination Polyhedron
The spatial arrangement of the ligands which are directly attached to the central atom or ion, is called coordination polyhedron around the central atom or ion.
7. Oxidation Number of Central Atom
The charge of the complex if all the ligands are removed along with the electron pairs that are shared with the central atom, is called oxidation number of central atom.
e. g., [ CU( CN4) 3-, oxidation number of copper is + 1, and represented as Cu( I).
Types of Complexes
1. Homoleptic complexes Complexes in which the metal atom or ion is linked to only one kind of donor atoms, are called homoleptic complexes e. g., [ Co( NH3) 6 ] 3 +
2. Heteroleptic complexes Complexes in which the metal atom or ion is linked to more than one kind of donor atoms are called heteroleptic complexes e. g., [ Co( NH3) 4CI2 ] +
3. Labile and Inert complexes
Complexes in which the ligand substitution is fast are known as labile complexes and in which ligand substitution is slow, are known as inert complexes.
Effective Atomic Number( EAN)
This concept was proposed by Sidgwick. In a complex, the EAN of metal atom is equal to the total number of electrons present in it.
EAN = Z – ON of metal + 2 * CN( where, Z = atomic