Question

The oxidation number of chlorine in $\text{KClO}$ is:
A. + 1
B. + 3
C. + 5
D. + 7

Answer 1

The oxidation state means the charge on the element in the compound. Write the common oxidation states of the known elements to find the oxidation state of the unknown element. Write the expression accordingly and solve the equation.

Complete step by step answer:
Let us first discuss the fixed oxidation states of common elements:
(1) All alkaline metals or the elements of group 1, exhibit oxidation state +1 in their corresponding compounds.
(2) All alkaline earth metals or the elements of group 2, exhibit oxidation state +2 in their corresponding compounds.
(3) The common oxidation state of oxygen element is -2.

Let us discuss the rules of writing the oxidation states and solve this question along with the rules:
(1) See the common oxidation states of a few elements in the given compound. Like, here
- Potassium $\left( \text{K} \right)$ belongs to group 1 as it is an alkaline metal. The oxidation state of potassium is +1.
- The oxidation state of oxygen $\left( \text{O} \right)$ is -2.

(2) See the overall charge on the given compound. Like,
The net charge on the compound $\text{KClO}$ is zero.

(3) To find the oxidation state of the required element; here $\left( \text{Cl} \right)$, the sum of oxidation states of all the elements multiplied to the number of atoms present of that element in the compound equals to the overall charge on the compound, here 0.

(4) Let the oxidation state of chlorine be x.
The expression will be $\left[ \left( 1\times 1 \right)+\left( 1\times \text{x} \right)+\left( 1\times -2 \right) \right]=0$.
The value of x will be + 1.
The oxidation state of chlorine in the compound is + 1.
The oxidation number of chlorine in $\text{KClO}$ is + 1.
So, the correct answer is “Option A”.

Note: The elements or non-metals with d-orbitals have variable oxidation states such as elements like $\text{S}$, $\text{Cl}$, $\text{P}$.
The common compounds formed by chlorine with different oxidation states are
$\text{ClO}_{4}^{-}$ has + 7 oxidation state, $\text{ClO}_{3}^{-}$ has + 5 oxidation state, $\text{ClO}_{2}^{-}$ has + 3 oxidation state and oxidation state of chloride ion $\left( \text{C}{{\text{l}}^{-}} \right)$ is -1. The oxidation states of chlorine vary from -1 to +7.