Question

Which has maximum polarizing power?
A. ${ Ca }^{ 2+ }$
B. ${ Cu }^{ 2+ }$
C. ${ Zn }^{ 2+ }$
D. ${ Sn }^{ 2+ }$

Answer 1

Hint: To answer this question we must know the two main factors on which the polarizing power is dependent. Those are the size and charge of the species. Now you may have an idea about the answer.

Complete step by step answer:
Here we should be aware that the polarising power of the cation depends upon two factors:
Size of cation: Smaller the size of cation, smaller is its polarizing power.
Charge on cation: As the charge on cation increases, its polarising power increases.
When a cation is able to distort an anion then it is known as polarizing power. The smaller is the size of a cation, the better it can hold the protons in its nucleus. As a result, the attraction between the nucleus and electrons will be strong. Hence, there will be shrinkage in size.
Each ${ Ca }^{ 2+ }$, ${ Cu }^{ 2+ }$, ${ Zn }^{ 2+ }$ are from the same period. Also, it is known that the size of atoms decreases on moving from left to right. Therefore, ${ Zn }^{ 2+ }$ will be the smallest of all.
Whereas ${ Sn }^{ 2+ }$ is larger in size as compared to the other molecules given in the options. Because it is from the fifth period. Therefore, it will have the least polarizing power.Thus, we can conclude that ${ Zn }^{ 2+ }$ has the highest polarizing power.
Therefore, the correct answer to this question is option C.

Note: There is another term Polarizability. Polarizability represents the ability of an anion to become polarized. In order for an anion to become polarized, its electron cloud must be distorted. This implies that the easier it is for an anion's electron cloud to be distorted, the more polarizable that anions are.