Question

What is the valency of iodine?

Answer 1

The property of an element which determines the combining power of an atom of that element, it determines the number of other atoms with which an atom of the element can combine to form a chemical compound.

Complete answer:
Iodine is a chemical element with atomic number $53$. It is a dark greyish or purple blackish element which is present in the halogen family of group 17 in the periodic table. Due to its larger size, it is the least reactive and most electropositive halogen. In brine pools and oceans, it is present as a water-soluble iodide on earth. It is not completely soluble in water but breaks down in some organic solvents like carbon tetrachloride ($CC{l_4}$).
The valency of the iodine can be calculated on the basis of the number of electrons present in its valence shell. To determine the number of valence electrons in iodine, we need to write its electronic configuration which is as follows:
Iodine (53) $= [Kr]4{d^{10}}5{s^2}5{p^5}$
As the number of electrons present in its valence shell $= 7$.
Therefore, the iodine atom needs one electron to complete its octet and to reach its nearest noble gas configuration. That means it has a tendency to accept an electron i.e., it will acquire a negative charge by accepting an electron.
Hence, we can conclude that the valency of iodine is $- 1$.

Note:
It is important to note that the valency of an atom may or may not have the same value as that of its oxidation number. Valency is the maximum number of electrons an atom can gain or lose whereas the oxidation number is the actual number of electrons the atom gained or lost while forming a molecule.