Question

Highest covalent character is found in which of the following?
(A)$Ca{{F}_{2}}$
(B)$CaC{{l}_{2}}$
(C)$Ca{{I}_{2}}$
(D)$CaB{{r}_{2}}$

Answer 1

Hint: Covalent character is analysed on the basis of fajans rule. When given questions have the same action, the tendency of anion decides the covalent character. More the ionic character, lesser the covalent character.

Complete answer:
Fajan’s rule is used to tell the covalent or ionic character of the given compound. According to fajan’s rule. No bond is purely covalent or ionic. Every ionic bond has some covalent character and every covalent bond has some ionic character present in it.
According to fajan’s rule, covalent character is more when,
(a)Ions have high charge in magnitude, that is cation has a greater positive charge and anion has a greater negative charge.
(b)Cation has small ionic radius
(c)Anion has large ionic radius
(d)Compounds of cation having $~{{s}^{2}},{{p}^{6}},{{d}^{10}}~$ configuration of outermost shell are largely covalent as compared to cation having the same size and charge but outer electronic configuration of ${{s}^{2}},{{p}^{6}}$ type.

In ionic compound cation, due to electrostatic force, attracts the electrons of anions. The tendency of cation to attract the electrons of anion is called polarizing power. When anions get attract towards the cation, the shape of the ions get distorted and anion is said to be polarized, or it is called polarisability of anion.Due to polarization, sharing of electrons take place and ionic compound has said to have some covalent character.

“Greater is the polarization, greater is the covalent character”.

For anions to get polarized, the size of an anion must be big enough, to get distorted by the cation, therefore, bigger the size of the anion , greater is the polarizability, greater is the covalent character.
In the given option in the question, Cation is the same with one positive charge, however, anions are different, therefore, bigger the anion, greater is the polarizability, greater is the covalent character.From the given options Iodide is the biggest anion.

So, the correct answer is “Option C”.

Note:
Polarising power of cation is directly proportional to the charge density of the cation. Charge density is the ratio of charge to volume. Polarisation of anion is the distortion of a symmetrically spherical electron cloud to an unsymmetric cloud.