Скачать с ютуб Q. What is Fajans rule/Covalent character in ionic compound/Polarisation? в хорошем качестве

Q. What is Fajans rule/Covalent character in ionic compound/Polarisation?

What is Fajans’ rule? We classify certain compounds as ionic and other compounds as covalent. Now if we were to ask the question, amongst the alkali chlorides, which is the most ionic? To answer these kinds of questions, we employ Fajans’ rules as a tool. Polarising power It is the extent to which a cation can polarise an anion. It is proportional to charge density. Charge density is the ratio of charge to volume. Polarising power α Charge density. More the charge density, greater is the polarising power for that cation. Polarisability It is the extent to which an ion can be polarised. It can also be called as the ease with which an ion can be polarised. Polarisation is the distortion of a spherically symmetric electron cloud to an unsymmetric cloud. Postulates of Fajans’ Rule The rule can be stated on the basis of 3 factors, which are: Size of the ion: Smaller the size of cation, the larger the size of the anion, greater is the covalent character of the ionic bond.The charge of Cation: Greater the charge of cation, greater is the covalent character of the ionic bond.Electronic configuration: For cations with same charge and size, the one, with (n-1)dn nso which is found in transition elements have greater covalent character than the cation with ns2 np6 electronic configuration, which is commonly found in alkali or alkaline earth metals. Examples on Fajans’ rule Illustration 1: Which compound should theoretically the most ionic and the most covalent amongst the metal halides? Solution: The smallest metal ion and the largest anion should technically be the most covalent Therefore, LiI is the most covalent. The largest cation and the smallest anion should be the most ionic. Therefore, CsF should be the most ionic.