Question

arrange the following cationsin the order of increasing polarising power

1. zn+2,cd+2,hg+2
2. cu+,ag+,au+,au+3

Answer 1

Dear User,
Polarising power of the cation depends upon two factor :

1. Size of cation : Smaller the size of cation, smaller is its polarsing power.
2. Charge on cation : As the charge on cation increases, its polarising power increases.

1) Zn^​2+, Cd²⁺, Hg²⁺
Since ll the ions have same charge, they can be arranged on the basis of their size. All theses elements belong to the same group and we know that size of element increases down the group. Order of their size in increasing order is : Zn<Cd<Hg
Therefore, order of increasing polarising power will be :Hg²⁺<Cd²⁺<Zn²⁺

2)Cu⁺, Au⁺, Ag⁺,Au³⁺
These all elements also belong to the same group. In increasing order of their size is : Cu<Ag<Au. Here, Au³⁺ is also present, the charge on this cation is high and so it will have the highest polarising power as compared to rest three monovalent ions. The rest three ions will be arranged on the basis of their size.
Therefore, order of increasing polarising power will be : Au⁺<Ag⁺<Cu⁺<Au³⁺