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.