Both Assertion and Reason are true but Reason is not the correct explanation of Assertion. Lithium ions have smaller size as compared to other ions of the group. Hence, it has greater value of charge to radius ratio and polarising power. Among alkali metals ions, Li has smallest size due to which it can easily polarise water molecule. LiCl contains 2 water molecules per mole. However, due to bigger size of other alkali metals, they cannot easily polarise water molecules.