The trend of attaining covalent character by ionic compounds as a consequence of polarisation may be generalized in terms of Fajan’s rule. According to this. Fajans’ Rule for the prediction of relative nonpolar character. Electrostatic forces in a crystal Learn Fajans’ Rule by Disclosing Covalent Characteristics in Ionic. Fajan Rule: Greater is the polarization, greater is the covalent character. | Online Chemistry tutorial IIT, CBSE Chemistry, ICSE Chemistry, engineering and.

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Let us consider AlI 3 ; this is an ionic bond which was formed by transfer of electrons. The deciding factor must be the cation. To picture how this occurs, compare the faians 1 where the electrons are evenly distributed and then consider 2 an instantaneous dipole that would arise from an uneven distribution of electrons on one side of the nucleus.

Because if this electron cloud of anion is more diffused.

Thus, we get an ionic compound metal bonded to a nonmetal with slight covalent character. They are a method for predicting ionic vs.

As the atoms in covalent compounds are held together by the shared electrons ,it is rigid and directional.

bond – What is Fajans rule? – Chemistry Stack Exchange

This results in synchronised motion of the electrons and an fajabs between them. This means a comparison needs to be made between a noble gas core and pseudo noble gas core, which as noted above holds that the pseudo noble gas would be the more polarizing.


The various types of these interactions span large differences in energy and for the halogens and interhalogens are generally quite small. Views Read Edit View history. Fajans’ rules note the difference were formulated in by Kazimierz Fajans. They are derived from momentary oscillations of electron charge in atoms and hence are present between all particles atoms, ions and molecules.

By using this site, you agree to the Terms of Use and Privacy Policy. For help asking a good homework question, see: The “size” of the charge in an ionic bond depends on the number of electrons transferred. We see fajqns a similar situation occurs, but instead of iodine we now have fluorine, a relatively small highly electronegative atom.

They usually consists of molecules rather than ions. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. How do I ask homework questions on Chemistry Stack Exchange?

Fajans’ rules – Wikipedia

This explains why for the common halides, iodides, rulea the most covalent in nature I – pm. Die Eigenschaften salzartiger Verbindungen und Atombau”. If two cations have the same size and charge, then the one with 18 electrons in the outermost shell has greater polarising power than the other with 8 electrons in the outermost shell. In this case, both fajas chlorides, so the anion remains the same.

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When a cation approaches an anion, the electron cloud of the anion is attracted towards a cation and hence gets distorted.

In general they increase with increasing atomic number. Electronic configuration of the cation: The ionic character arises from gajans polarizability and polarizing effects of H and I. Chemistry Stack Exchange works best with JavaScript enabled.

Fajans’ Rule – Disclosing Covalent Characteristics in Ionic Bonds

What Is Valence Bond Theory. Retrieved from ” faajns This page was last edited on 18 Novemberat In the time with the help of X-ray crystallography, he was able to predict ionic or covalent bonding with the attributes like ionic and atomic radius. On the left, the cation charge increases size decreases and on the right, the anion size increases, both variations leading to an increase in the covalency. By Fajans’ Rules, compounds are more likely to be ionic if: Two contrasting examples can illustrate the variation in effects.

In reality, every bond has some covalent as well as ionic characteristics. This question appears to be off-topic. Both a and b. Take learning on the go with our mobile app.