$6\mathrm{.}4$ Stability constants $(lo{g}_{10}{K}_1)$ for complex formation between some $2+$ metal cations

and sulphate $(S{O}_4^{2-})$ and thiosulphate $(S_2{O}_3^{2-})$ are tabulated below. On the basis of

these data, classify the three cations according to the "Hard and Soft Acids and

Bases" principle. Which do you expect to be the donor atom of the thiosulphate in

each case?