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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Practise s of questions mapped to your syllabus. They are derived from momentary oscillations of electron charge in atoms and hence are present between all particles atoms, ions and molecules.

Fajan’s Rules

Two contrasting examples can illustrate the variation in effects. Thus, we get an ionic compound metal bonded to a nonmetal with slight covalent character. Comments It is very urles thak u very much!!! The greater is the polarisation produced, more is the neutralisation of the charges and hence the ionic character decreases or the covalent character increases. What is Fajans rule? In this article, we are going to discuss covalent characteristics in ionic bonds.

Covalent compounds have low melting rulew boiling point because the molecules in covalent compounds are held together less rigidly. In the case of aluminium iodide an ionic bond with much covalent character is present. Based on Fajan’s rules, it fajams expected that every ionic compound will have at least some amount of covalent character.


Compounds are more likely to be covalent if: 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. They are generally soluble in organic solvents but insoluble in water and other polar solvents.

The “size” of the charge in an ionic bond depends on the number of electrons transferred. The deciding factor must be the cation. The large charge pulls on the electron cloud of the iodines.

From Wikipedia, the free encyclopedia. In inorganic chemistryFajans’ rulesformulated by Kazimierz Fajans in[1] [2] [3] are used to predict whether a chemical bond will be covalent or ionicand depend on the charge on the cation and the fahans sizes of the cation and anion.

Fajans’ rules – Wikipedia

Boiling Point Of Oxygen. Larger the charge on the cation, greater is its polarising power. 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.

From the Table below the observed dipole moment of KBr is given as When two molecules are close together, the instantaneous dipole of one molecule can induce a dipole in the second molecule. These compounds are molecular in nature and not ionic, their reactions are molecular and proceed at a much slower rate than those of ionic compounds. Because if this electron cloud of anion is more diffused. Gas To Solid Is Called.


From this it is possible to calculate a theoretical dipole moment for the KBr molecule, assuming gajans charges of one fundamental unit located at each nucleus, and hence the percentage ionic character of KBr. Login to track and save your performance. Your email address will not be published. Jj Thomson Atomic Theory. The crystal structure of covalent compounds differ from that rues ionic compounds. Retrieved from ” https: Let us consider AlI 3 ; this is an ionic bond which was formed by transfer of electrons.

The various types of these interactions span large differences in energy and for the halogens and interhalogens are generally quite small. They usually consists of molecules rather than ions. Note that Fajans’ Rules have been largely displaced by Pauling’s approach using electronegtivites.

The forces involved in these cases are called London dispersion forces after Fritz Wolfgang London, Since there are no free ions in covalent compounds to conduct electricity, they are bad conductors of electricity. The polarizing power and polarizability that enhances the formation of covalent bonds is favoured by the following factors: The ability of a cation to distort an anion is known as its polarization power and the tendency of the anion to become polarized by the cation is known as its polarizability.