Question

Find the oxidation state of Mn in $Mn{O_4}^{-}$.

Answer 1

Hint: Oxidation state is also known as the oxidation number. The oxidation state can be found out by equating the oxidation number of each molecule by the overall charge of the complex. The oxidation number may be negative zero or positive.

Complete-step- by- step answer:
As we know that the oxidation number is the number of electrons lost or gained from a molecule in order to form a chemical bond with another molecule.
If the molecule loses an electron, it means it lost a negative charge then the molecule becomes positively charged.
If the molecule gains an electron, which means it gained a negative charge hence the molecule becomes negatively charged.
Therefore, to find the oxidation state of manganese in $Mn{O_4}^{-}$, firstly we will consider the oxidation number on Mn to be x.
As we can see, there is an overall charge of -1 in the given ion therefore the total sum of the oxidation number of all the elements present will be equal to -1.
Charge on a single oxygen atom is -2.
Therefore, we can write that-
$\begin{array}{rl}& x+4\times (-2)=-1\\ & \Rightarrow x=-1+8=+7\end{array}$

Therefore, the Mn in $Mn{O_4}^{-}$ is in a +7 oxidation state.

Additional Information: The increase in oxidation number of an atom undergoing a chemical change is referred to as oxidation and a decrease in the oxidation number is referred as reduction. However, for pure elements, the oxidation number is zero, they are neutral.

Note: It is important to remember the charge on atoms in order to find out the oxidation state. Like, the charge of oxygen is -2 and that for hydrogen is +1 generally but when oxygen is bonded to a more electronegative element it is +2 and when hydrogen is bonded with less electronegative element charge is -1.