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