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.

Author: Brara Samular
Country: Guyana
Language: English (Spanish)
Genre: Education
Published (Last): 3 October 2018
Pages: 173
PDF File Size: 15.76 Mb
ePub File Size: 17.57 Mb
ISBN: 414-2-62769-155-6
Downloads: 6006
Price: Free* [*Free Regsitration Required]
Uploader: Mausar

The forces involved in these cases are called London dispersion forces after Fritz Wolfgang London, Fules 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.

Fajans’ rules

Jj Thomson Atomic Theory. The deciding factor must be the cation.

This question appears to be off-topic. To picture how this occurs, compare the situation 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. By using this site, you agree to the Terms of Use and Privacy Policy.

Thus, we get an ionic compound metal bonded to a nonmetal with slight covalent character.

They can be summarized in the following table: As the atoms in covalent compounds rulrs held together by the shared electrons ,it is rigid and directional. 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 relative sizes of the cation and anion.


Compounds are more likely to be covalent if: They are a method for predicting ionic vs. To use Fajanw Rules, assume your binary compound is ionic and identify the potential cation and anion.

Fajans’ Rule – Disclosing Covalent Characteristics in Ionic Bonds

As the electron cloud of the iodine nears the aluminium atom, the negative charge of the electron cloud “cancels” out the positive charge of the aluminium cation. In reality, every bond has some covalent as well as ionic characteristics. The greater is the fajas produced, more is the neutralisation of the charges and hence the ionic character decreases or the covalent character increases.

Chemistry Stack Exchange works best with JavaScript enabled. The effect is called polarisation of the anion. Home Questions Tags Users Unanswered. Boiling Point Of Oxygen. Intermolecular forces are the attractive forces between molecules without which all substances would be gases.

Fajans’ rules – Wikipedia

Covalent character of lithium halides is in the order:. Views Read Edit View history. Fajans’ rule states that a compound with low positive charge, large cation and small anion has ionic bond where as a compound with high positive charge, small cation and large anion are covalently bonded. How do I ask homework questions on Chemistry Stack Exchange? That positive charge then exerts an attractive force on the electron cloud of the other ion, which has accepted the electrons from the aluminium or other positive ion.


They are generally soluble in organic solvents but insoluble in water and other polar solvents.

Your email address will not be published. They are derived from momentary oscillations of electron charge in atoms and hence are present between all particles atoms, ions and molecules.

From an MO perspective, the orbital overlap disperses the charge on each ion and so weakens the electrovalent forces throughout the solid, this can be used to explain the trend seen for the melting points of lithium halides.

In this case, the aluminium ion’s charge will “tug” on the electron cloud of iodine, drawing it closer to itself. Two contrasting examples can illustrate the variation in effects.

This explains why for the common halides, iodides, are the most covalent in nature I – pm. What is Fajans rule? For help asking a good homework question, see: