JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Chemical Bonding and Molecular Structure

Fajans' rules describe what raises the covalent character of an ionic bond, the central idea being that the cation distorts the anion's electron cloud. The polarising power of the cation, listed as (a), is a factor, since a small, highly charged cation pulls strongly on the anion. The extent of distortion of the anion, listed as (b), is a factor, because the degree to which the anion's electron cloud is distorted is precisely what covalent character measures. The polarisability of the anion, listed as (c), is a factor, since a large, loosely held electron cloud is distorted easily. The polarising power of the anion, listed as (d), is not a factor, because the anion is the species being polarised, not the one doing the polarising. Three of the listed factors apply.