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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This question appears to be off-topic. Larger the charge on the cation, greater is its polarising power.

For fzjans asking a good homework question, see: By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The percentage of ionic character in a compound can be estimated from dipole moments.

Whilst not strictly true for heteronuclear molecules it does provide a simple qualitative method for predicting the bond character. From this it is possible to calculate a theoretical fajxns moment for the KBr molecule, assuming opposite charges of one fundamental unit located at each nucleus, and hence the percentage ionic character of KBr. What Is Valence Bond Theory. They are derived from momentary oscillations of electron charge in atoms and hence fajsns present between all particles atoms, ions and molecules.

Fajan’s Rules

What is Fajans rule? Chemistry Chemistry Articles Fajans Rule.


On average the electron cloud for cajans can be considered to be spherical in shape. Take learning on the go with our mobile app. Hence, atoms in a molecule can take up different directional arrangement and thus show structural and stereoisomerism. 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. Now, if we consider the iodine atom, we see that it is relatively large and thus the outer shell electrons are relatively well fajanss from the nuclear charge.

When two non-polar molecules approach, attractions or repulsions between the electrons and nuclei can lead to distortions in their electron clouds i.

Fajans’ rules – Wikipedia

They can be summarized in the following table:. When the melting points of two compounds are compared, the one having the lower melting point is assumed to have the smaller degree of ionic character. The various types of these interactions span large differences in energy and for the halogens and interhalogens are generally quite small.

They are a method for predicting ionic vs. The ability of a cation to distort an anion is known as its polarization rues and the tendency of the anion to become polarized by the cation is known as its polarizability.

Fajans’ rules

Compounds are more rulees to be covalent if: Covalent compounds have low melting and boiling point because the molecules in covalent compounds are held together less rigidly. Electronic configuration of the cation: Views Read Edit View history.


Practise This Question The acid formed when sulphur trioxide reacts with water is. This results in synchronised motion of the electrons and an attraction between them. Now, if we take a different example, for example AlF 3 Aluminium Fluoride. The polarising power of the cation and the polarisability of the anion and hence the formation of covalent bond depends on:. They usually consists of molecules rather than ions. Leave a Reply Cancel reply Your email address will not be published.

fjaans 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.

This makes the anion easily polarizable. The covalent compounds exist in all the three states i.

Fajans Rule | Disclosing Covalent Characteristics In Ionic Bonds

When two molecules are close together, the instantaneous dipole of one molecule can induce a dipole in the second molecule. In reality, every bond has some covalent as well as ionic characteristics.

Intermolecular forces are the attractive forces between molecules without which all substances would be gases.

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