Question

LiI is less stable than CsI. Why?​

Answer 1

LiI is less stable than CsI because of the following fact:--

We know that as we move down the group number of shell increases due to increase in number of shell size of atom increases as the distance between outermost shell and nucleus increases so size increases down the group.

Since Li and Cs belong to same group so as we move down size increases and hence size of Cs is greater than size of Li and iodine as it belongs to down most position of halogen so is large in size.

Hence both anion and cation which are large in size have greater polarizing ability than cation of small size and anion of large size .

Also by fajan rule for ionic bond size of cation should be large and charge small so Cs has more size than Li hence form stable ionic bond.

Hence as cation and anion both are large in CsI hence CsI is stable than LiI.