TABLE OF CONTENTS It is well known that when an acid reacts with an alkali, a neutralization reaction occurs and a simple salt is formed as:
Also, when solutions containing two or more salts in simple proportions are allowed to evaporate, two types of addition compounds are formed. For example,
Double salt. These salts give test of all constituents i.e., individual components do not lose their identity. For example,
Coordination compounds. In these compounds individual components lose their identity and a complex ion is formed. For example, when solutions of Fe(CN) 2 and KCN are mixed and evaporated, potassium ferrocyanide is formed as:
The other examples of such compounds are
Thus, a complex ion is defined as an electrically charged radical formed by the union of a metal cation with one or more neutral molecules or anions.
Coordination number (CN). The total number of the ligands that can coordinate to the central metal ion is the coordination number of the metal cation. Numerically, it represents the total number of chemical bonds formed between the central metal ion and donor atoms of the ligand. For example, in ferrocyanide [Fe(CN) 6] 4? ion, the coordination number is 6.
Some common coordination numbers are 2, 3, 4, and 6. The lighter transition metals generally exhibit 4 and 6 coordination numbers while the heavier transition elements generally exhibit coordination number greater than 6, i.e., 7 or 9. Certain metals have been found to possess...
