Question

Polarisation involves the distortion of the shape of an anion by an adjacent cation. In this context, which of the following statements is correct?

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

Answer 1

The correct option is A Maximum polarisation is brought about by a cation of high charge

(a) From Fajan's rules, greater the charge on the cation, more is its polarizing power.
For example, the decreasing order of the polarisation is
$SiC{l}_4>AlC{l}_3>MgC{l}_2>NaCl$

(b) Smaller the radius of the cation, higher is its polarisation power.

(c) A smaller cation has more polarising power.
For example, the decreasing order of polarisation is
$LiCl>NaCl>KCl>RbCl>CsCl$

(d) The term polarisation power is applicable to cations and the term polarisability is applicable to anions.