FAZAN'S RULES

FAZAN'S RULES  :- 

Rules regarding polarization are known as Fajan's rule. According to Fajan's rules.

1.the cations with smaller size have high polarising power i.e, they polarise or distort the electron cloud of anion to greater extent because smaller cation has high charge density.the cations with large size size has low polarizing power.

2.The anion with large size have high polarisability,i.e, their electron cloud can be easily distorted by the cation.

3. there should be high charge on the cation or anion for effective polarization. the highly charged cation bill exert greater effect in polarising anion and highly charged anion will be easily polarised.

4. cations with non–inert gas configuration for transition element(ns² p⁶ d¹⁰) have high polarising power than cations with noble gas configuration i.e, ns² np⁶. for example cu+ ion is more effective in polarising the anion than the anion than Na+. this is because the electrons of 3D subshell of sodium ion.thus there is greater effective nuclear charge in Cu+ ion on anion which is distorted to a greater extent.now polar character increase more in case of compounds containing cation Cu+ than compounds containing Na+ ion 

 5. Solvent of high dielectric constant decreases the electrostatic attraction between the ion and there decreases the tendency of form covalent bond.

6. higher the value of ionic potential of the cation, greater is its polarizing power thun increasing the covalent character of a bond. ionic potential is the ratio of charge to radius of a cation.

 application of faizan's rule 

1. Bromides and iodides have higher lattice energies or higher stabilities then expected. this extra stability is due to large size of anion which causes greater polorization result in the formation of polar covalent bond which is more stable than pure ionic bond.

2. the solubility of ionic compound in polar solvent decreases with increase in extent of the polarisation for e.g. LiCl is soluble in nonpolar solvents whereas other alkyl halides are insoluble.

3. tendency to form solvated compound increases with increase in the value of ionic potential or smaller the size of cation, greater its tendency to form solveted compound. for example lithium forms compound such as LiCL.2H2O and LiCLO4.3H2O.

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