Question

The correct increasing order of covalent character of LiCl, LiBr, LiI is :
a.) LiI < LiBr < LiCl
b.) LiCl < LiI < LiBr
c.) LiI < LiCl < LiBr
d.) LiCl < LiBr < LiI

Answer 1

Hint: The Lithium ion being small in size can easily distort the electron cloud of an anion thereby leading to the formation of a covalent bond. As the lithium is small in size, higher is the size of anion; higher will be the covalent character in bond. So, the increasing order of covalent character will be the same as that of increasing order of the size of halides.

Complete step by step answer :
First, let us see what a covalent character is. The covalent character of a bond may be defined as the measure of polarization of the bond. More is the polarization in a bond, lower is the value of its covalent character. For example - In HCl, the bond between H atom and Cl atom, it has its electrons attracted more towards Cl atom instead of equal sharing. This is because Cl is more electronegative than H. So, this bond has more ionic and less covalent character. The Fazans rules govern the formation of a covalent bond between two atoms.
The Fazans rules state that the cations with small size combine with anions of larger size to form a covalent bond.
Li-ion is small in size and it can combine with halides which normally have larger sizes. The lithium halides thus have partial covalent character. From, the above options given we have three halides as - I, Cl and Br.
These can be arranged in decreasing order of their sizes as -
I > Br > Cl
Larger is the size of anion, more will be the covalent character of the bond it will form with Lithium.
Thus, the decreasing order of covalent character among halides is as -
LiI > LiBr > LiCl
Or the increasing order of the covalent character is -
LiCl < LiBr < LiI

So, the option d.) is the correct answer.

Note: It must be noted that the covalent bond and ionic bond both are different things. The covalent bond is formed by equal sharing of electrons while in an ionic bond, the electrons are donated. Each bond is formed of some covalent character while the other left ionic character. If an ionic character is more, the covalent character will be less and vice versa.