Question

Polarisation is the distortion of the shape of an anion by an adjacently placed cation. Which of the following statements is correct?

• A. Maximum polarisation is brought about by a cation of high charge
• B. Maximum polarisation is brought about by a cation of low radius
• C. A large cation is likely to bring about a large degree of polarisation
• D. Polarising power of a cation is less than that of anion

Answer 1

Answer: (A), (B)

The correct options are
A Maximum polarisation is brought about by a cation of high charge
B Maximum polarisation is brought about by a cation of low radius

The statements C and D are incorrect.
(A) Higher is the charge, higher is the polarization power.
For example, the decreasing order of the polarization power is
$SiC{l}_4>AlC{l}_3>MgC{l}_2>NaCl$
(B) Lower is the radius of the cation, lower is the size of the cation and higher is the polarisation power.
(C) Smaller cation has more polarization power.
For example, the decreasing order of the polarization power is
$LiCl>NaCl>KCl>RbCl>CsCl$
(D) The term polarisation power is applicable to the cation and the term polarizability is applicable to anion.