Question

Why is $LiCl$ more covalent than $KCl$ .

Answer 1

We know that an anion is an ion that has gained one or more electrons, acquiring a negative charge. A cation is an ion that has lost one or more electrons, gaining a positive charge. The covalent character depends upon the size of the cation and size of anion. Also, the covalent character is inversely proportional to the electronegativity difference and similar atoms have the least electronegativity difference. Therefore, they have the maximum covalent character. Using Fajan’s rule we find which is more covalent.

Complete answer:
The tendency of the anion to become polarized by the cation is known as its polarizability. Smaller is the size of the cation and higher will be its charge density, which means greater concentration of charge on a smaller area. Therefore, the polarizing power of a cation is inversely proportional to its size. Hence the covalent character is proportional to the polarizing power of a cation.
Fajan’s rule states that the larger the cation size lesser is the covalent character. Here the anion $C{l^ - }$ is the same, but the cation $L{i^ + }$ is much smaller than ${K^ + }$ ion. So, more polarization occurs in $LiCl$ than $KCl$ . Hence $KCl$ has less covalent character than $LiCl$ .
Hence $LiCl$ is more covalent than $KCl$ .

Note:
Note that if the degree of polarization is quite small, an ionic bond is formed, while if the degree of polarization is large, a covalent bond is formed. In covalent bonds, atoms share electrons, whereas in ionic bonds atoms transfer electrons. The reaction components of covalent bonds are electrically neutral, whereas for ionic bonds they are both charged.