Valency of iron in \[FeC{{l}_{2}}\]……... is and in \[FeC{{l}_{3}}\], it is ………?
a.) 3,2
b.) 3,4
c.) 2,3
d.) 2,4

Hint: Valency is the combining capacity of an element or we can say the number of hydrogen atoms it can displace or combine with. Transition metals like Iron (Fe) and Copper (Cu) show more than one valency in compound formation.

Complete step by step solution:

To find the valency we must need to know the electronic distribution of the given element.
For example, the atomic number of Oxygen is 8. And its electronic configuration is K=2, L=6.
You can see it has 6 electrons in its outermost shell and it needs two more electrons to complete its octet. So, its valency is 2.
Now in this case, chlorine has 7 valence electrons in its outermost shell and it needs 1 more electron to complete its octet.
But in \[FeC{{l}_{2}}\] , iron is combined with two chlorine atoms so it donates two electrons to two chlorine atoms.
Thus, the valency of Iron (Fe) here is 2.
Similarly, in the case of \[FeC{{l}_{3}}\], iron combines with three atoms of chlorine and each requires one electron to complete its octet. So, iron donates 3 electrons. One for each chlorine atom.
Thus, the valency of Iron (Fe) here is 3.

Therefore, the correct answer will be (c).

Note: Always remember valence electrons and valency is two different things. Valence electrons is the number of electrons present in the outermost shell. Whereas valency is the number of electrons an element can gain or lose to combine with another element.
For example:
Fluorine has 7 valence electrons. But its valency is 1 because it gains one electron to combine with other elements.