Question

According to Fajan’s rule, covalent bond is favoured by:

• A. Small cation and large anion
• B. Small cation and small anion
• C. Large cation and large anion
• D. Large cation and small anion

Answer 1

The correct option is A

Small cation and large anion

Explanation:

Fajan’s rule is a collection of factors for assessing whether a bond is covalent or ionic. The size, charge, and electronic configuration of ions influence their covalent character, with larger anion having a stronger covalent character than cation.

Postulates of Fajan's Rule:

The rule can be stated on the basis of 3 factors, which are:

(1)Size of the ion: Smaller the size of cation, the larger the size of the anion, greater is the covalent character of the ionic bond.

(2)The charge of Cation: Greater the charge of cation, greater is the covalent character of the ionic bond.

(3)Electronic configuration: For cations with same charge and size, the one, with (n-1)dⁿ ns^o which is found in transition elements have greater covalent character than the cation with ns² np⁶ electronic configuration, which is commonly found in alkali or alkaline earth metals.

Therefore, the correct option is (A)