Question

Oxidation state of Fe in $F{{e}_{3}}{{O}_{4}}$ are:
Options are-
(A) + 2 and + 3
(B) + 1 and + 2
(C) + 1 and + 3
(D) None

Answer 1

Hint: An attempt to this question can be made by drawing the expanded structure of the compound. Determine the oxidation state of atoms attached with Fe atoms in the compound. Based on that, determine the oxidation state of iron atoms such that the overall electric charge on the compound cancels out making the compound electrically neutral.

 Complete answer:
We will start the solution by understanding the composition of $F{{e}_{3}}{{O}_{4}}$.
$F{{e}_{3}}{{O}_{4}}$ is made up of two oxides of iron namely, Iron(II) oxide and (III) oxide.
We will now draw the expanded structure of both these compounds and determine the oxidation state of iron in these two compounds.
Iron (II) oxide :

In the structure above we see that the Fe atom is attached to one oxygen atom. The oxidation state of oxygen is -2. So, the oxidation state becomes +2. This is because the total electric charge on the compound should be 0.
Iron (III) oxide :

In the structure above we can identify 3 oxygen atoms attached to 2 Fe atoms. The oxidation state of oxygen is -2. Thus, the oxidation state of Fe becomes +3. This is done in order to balance out the charge to make the compound electrically neutral.
Thus, the Oxidation state of Fe in $F{{e}_{3}}{{O}_{4}}$ are:
+ 2 and + 3

 The correct answer is option (A).

 Note:
It is important to know that the oxidation state of Fe is +3 in Iron(III) oxide and not 6. This is because the -6 charge has to be balanced by 2 Fe atoms. Thus the oxidation state of both the Fe atoms is +3.