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(a) Describe Fajan's rule

Answer» <html><body><p></p>Solution :(a) The ability of a cation to polarise an anion is called its polarising ability and the tendency of an anion to get polarised is called its polsrisability. The <a href="https://interviewquestions.tuteehub.com/tag/extent-981159" style="font-weight:bold;" target="_blank" title="Click to know more about EXTENT">EXTENT</a> of polarisation in an ionic compound is given by the Fajans rules <br/> Fajans Rules : <br/> (1) To show greater covalent character, both the cation and anion should have high charge on them. Higher the positive charge on the cation, grater will be the attraction on the electron cloud of the anion. Similarly higher the magnitude of nagative charge on the anion, greater is its polarisability . Hence, the increase in charge on cation or in anion increases the covalent character <br/> Let us <a href="https://interviewquestions.tuteehub.com/tag/consider-2017521" style="font-weight:bold;" target="_blank" title="Click to know more about CONSIDER">CONSIDER</a> three jonic compounds <a href="https://interviewquestions.tuteehub.com/tag/aluminum-858890" style="font-weight:bold;" target="_blank" title="Click to know more about ALUMINUM">ALUMINUM</a> chloride, magnesium chloride and sodium chloride. Since the charge of the cation increase in the order `Na^(+) lt Mg^(2+) lt Al^(3+)`, the covalent character also follows the same order `NaCl lt MgCl_(2) lt AlCl_(3)`. <br/> (ii) The smaller cation and larger anion show greater covalent character due to the grater extent of polarisation. <br/> Lithium chloride is more covalent than sodium chloride e size of `Li^(+)` is smaller than `Na^(+)` and hence the polarising power of `Li^(+)` is more. Lithium iodide is more covalent than lithium chloride as the size of `I^(-)` is larger than the `Cl^(-)`. Hence `I^(-)` will be more polarised than `Cl^(-)` by the cation , `Li^(+)`. <br/> (iii) Cations having `ns^(2) np^(6) nd^(10)` configuration show greater polarising power than the cation with `ns^(2) np^(6)` configuration. Hence, they show greater covalent character. <br/> `CuCl` is more covalent than `NaCl`. Compared to `Na^(+) (1.13overset(" "@)(A))`. `<a href="https://interviewquestions.tuteehub.com/tag/cu-428205" style="font-weight:bold;" target="_blank" title="Click to know more about CU">CU</a>^(+)(0.6 overset(" "@)(A))` is smalland have `3s^(3) 3p^(6) 3d^(10)` conguration <br/> Electronic conguration of `Cu^(+)` <br/> [Ar] `3s^(2), 3p^(6), 3d^(10)` <br/> Electronic Conguration of `Na^(+)` <br/> [He] `<a href="https://interviewquestions.tuteehub.com/tag/2s-301125" style="font-weight:bold;" target="_blank" title="Click to know more about 2S">2S</a>^(2), p^(6)`</body></html>


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