ABSTRACT
When a central metal atom or ion is surrounded by a cluster of ligands a complex compound or an ion is formed. The charge on the complex ion is equal to the sum of the charges on the metal ion and the ligand. If the ligand happens to be a molecule or compound its charge is taken as zero. The central metal ion and the ligands which are closely attached to it inside the square bracket are called by Werner the first coordination sphere. The anions outside the square bracket form the second sphere of attraction. The ligands are closer to the metal ion inside the square bracket. The arrangement between the metal ion and the ligand is fixed in space i.e., linear, triangular, tetrahedral, square planer, square pyramid, trigonal bipyramidal, and octahedral.
