Why lithium iodide is covalent but potassium iodide is ionic?
Answers
Explanation:
In case of lithium iodide, cation is lithium and anion is iodine. Size of lithium ion is very small whereas size of iodine ion is very large.
Thus, according to Fajan's rule smaller is the size of cation more will be its polarizing power and larger is the size of anion more will be its polarizability. Hence, this results in the formation of covalent bond.
Therefore, due to large size of iodine ion its valence electrons will be loosely held by nucleus. So, lithium ion will easily polarize the iodine electrons which results in sharing of electrons. Thus, covalent bond will be formed.
In case of potassium iodide, size of potassium ion and iodine ion are almost similar in size. Therefore, potassium ion will not be able to polarize iodine ion. So, there will be transfer of electron. As a result, ionic bond will be formed.