Question

how does the charge-radius ratio of lithium ion differ from those of other group 1A ions?

Answer 1

It has been seen that Li differs from other alkali metal in many respects and shows a close resemblance to Mg (diagonal relationship), the second element of group-2 and diagonally opposite to Li in the periodic table. On moving diagonally in the periodic table, the polarising power i.e. ratio of the ionic charge and square of the ionic radius is nearly same for the Lithium and Magnesium (ionic charge and ionic radius of Li and Mg are +1 and +2 and 60pm and 65pm respectively) and accounts for the similarities between the properties of the two elements.