what is Fazan rule? ?
Answers
Answer:
formulated by Kazimierz Fajans in 1923,are used to predict whether a chemical bond will be covalent or ionic, and depend on the charge on the cation and the relative sizes of the cation and anion. They can be summarized in the following table:
Explanation:
Thus sodium chloride (with a low positive charge (+1), a fairly large cation (~1 Å) and relatively small anion (0.2 Å) is ionic; but aluminium iodide (AlI3) (with a high positive charge (+3) and a large anion) is covalent.
Polarization will be increased by:
high charge and small size of the cation
Ionic potential Å Z+/r+ (= polarizing power)
High charge and large size of the anion
The polarizability of an anion is related to the deformability of its electron cloud (i.e. its "softness")
An incomplete valence shell electron configuration
Noble gas configuration of the cation produces better shielding and less polarizing power
e.g. Hg2+ (r+ = 102 pm) is more polarizing than Ca2+ (r+ = 100 pm)
Explanation:
Fajans rule explains polarising power : CATION. It says that as the charge density on metal cation increase it forms ionic compound with large covalent character . polarising power of cation depends on charge density of cation. i.e., smaller the size and greater the charge, more will be polarising power.