Coordination compounds are those addition molecular compounds which retain their identity in solid state as well as in dissolved state . In these compounds the central metal atom or ion is linked by ions or molecules with coordinate bonds . e . g ., Potassium ferrocyanide , K4 [ Fe ( CN ) 6 ].
Double Salts
These are the addition molecular compounds which are stable in solid state but dissociate into
constituent ions in the solution . e . g ., Mohr ’ S salt , [ FeSO4 ·( NH4 ) 2SO4 . 6H2O get dissociated into Fe2 +, NH + 4 and SO2-4 ions .
Terms Related to Coordination Compounds 1 . Complex ion or Coordination Entity
It is an electrically charged species in which central metal atom or ion is surrounded by number of ions or neutral molecules .
Cationic complex entity It is the complex ion which carries positive charge . e . g ., [ Pt ( NH3 ) 4 ] 2 +
Anionic complex entity It is the complex ion which carries negative charge . e . g ., [ Fe ( CN ) 6 ] 4-
2 . Central Atom or Ion
The atom or ion to which a fixed number of ions or groups are bound is . ned central atom or ion . It is also referred as Lewis acid . e . g ., in ( NiCI2 ( H2O ) 4 ]. Ni is central metal atom . It is generally transition element or inner-transition element .