Question

The polarising power of a cation is directly proportional to its size.
A. True
B. False

Answer 1

Hint: In order to find the relation between the cation size and the polarizing power, we should be clear about the concept of charge density. The relation of charge density with polarizing power will help us to solve this question.

Complete step-by-step answer:
The polarizing power of a cation is inversely proportional to its size. Smaller is the size of the cation and higher will be its charge density, which means greater concentration of charge on a smaller area. The more will be the charge density, higher will be its polarising power. Thus, among the alkali metal cations lithium ions have a smaller size and highest polarising power.

Therefore the question which states that the polarizing power of a cation and is directly proportional to its size is false.

So the correct answer is Option B.

The order of the polarizing power of the cations starts with Lithium (having the highest polarizing power), then Sodium, Potassium, Rubidium and then Caesium (having the lowest polarizing power).

Additional Information:
The magnitude of polarization or increased covalent character depends upon a number of factors: These factors are size of the cation, electronic configuration of the cation, covalent character, reactivity of metals and metalloids, catenation, multiple bonds,bond character based on electronegativity differences etc.

Note: The ability of a cation to distort an anion is known as its polarization power and the tendency of the anion to become polarized by the cation is known as its polarizability.