Query related to "Fajans Rule" - Class 11



Does more covalent character leads to more solublity? Justify.


Normally, ionic compounds are higher melting, higher boiling, more water soluble. Are you sure your qs “more covalent character leads to more solublity” has answer in affirmative?


actually we have to give justification to the question that yes covalent ccharcter leads to more solubility?


Check https://en.wikibooks.org/wiki/Introduction_to_Inorganic_Chemistry/Ionic_and_Covalent_Solids_-_Energetics#.C2.A0.C2.A09.10_Lattice_energies_and_solubility

  1. Increasing covalency leads to lower solubility in the salts (due to larger EL. For example, AgF, AgCl, AgBr, and AgI exhibit progressively lower solubility because of increasing covalency.

AgF > AgCl > AgBr > AgI

Also the book “Fundamentals of Inorganic Chemistry”, check this page (click here)


Although atomic bond in a compound like M+X- is considered to be 100% ionic, actually it also has some covalent character. An explanation for the partial covalent character of an ionic bond has been given by Fajan. According to Fajan, if two oppositely charged ions are brought together, the nature of the bond between them depends upon the effect of one ion on the other.

When two oppositely charged ions (say A+ and B- ) approach each other the positive ion attracts electrons on the outermost shell of the anion and repels its positively charged nucleus. This results in the distortion,deformation or polarization of the anion. If the polarization is quite small, an ionic bond is formed, while if the degree of polarization is large, a covalent bond results.

Thus the power of an ion (cation) to distort the other ion is known as its polarization power and the tendency of the ion(anion) to get polarized by the other ion is known as its polarisability. Greater the polarization power or polarisability of an ion, greater will be its tendency to form a covalent bond.
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