Question

What are the oxidation numbers for $Cl{{O}^{-}}$?

Answer 1

Before answering this, we should first know how to find the oxidation number. Oxidation state or oxidation number of atom and ion is obtained by – Adding up the constant oxidation state of other atoms that are bonded to it. The total charge of the molecule is equated to the total oxidation state of a molecule.

Complete answer:
The number that is given to the elements in a chemical combination. The calculation of the number of electrons that are shared gained and lost by atoms in a molecule while chemically bonded with other atoms of a different element. The other name of the oxidation number is oxidation state. It could also have different references if the electronegativity of atoms is considered. In coordination chemistry, the Oxidation number is used a lot. It is simply the number of electrons an atom has been gained, lost, or shared with the neutral atom. Group 1, 2, and 3 have electropositive atoms who always lose a fixed number of electrons and the oxidation number is positive constantly.
$Cl{{O}^{-}}$ is the hypochlorite anion, we know that the atom which makes up the anion should have an oxidation state -1.
The overall charge of the ions :
$O{{N}_{chlorine}}+O{{N}_{oxygen}}=-1$
As we know, oxidation numbers are linked to electronegativity. The concept is that the more electronegative atom will take the electrons from the bond with the less electronegative atom.
When oxygen is bonded with a less electronegative atom, The oxidation state equals 2.
So, we can say here oxygen is more electronegative if we compare it with chlorine.
Therefore,
$O{{N}_{chlorine}}+(-2)=-1$
$O{{N}_{chlorine}}=-1+2=1$
The oxidation number of atoms forming the anion are :
$Cl\,=\,+1$
${{O}^{-}}=-2$

Note:
In the case of molecules, the more electronegative atom gains an electron from the atom which is less electronegative and it has a negative oxidation state. The number of electrons gained or lost is equal to the oxidation state.