Chapter 19, Problem 18E

Interpretation Introduction

Interpretation:

The oxidation number of the underlined species in $\underset{\_}{\text{C}}{\text{O}}_2,{\underset{\_}{\text{Cr}}}_2{\text{O}}_7^{2-},{\underset{\_}{\text{Cl}}}^{-}$ is to be stated.

Concept introduction:

A species gain or loses electrons to form anions or cations respectively. To keep a track on the loss or gain of an electron, a number is assigned in the form of oxidation number. The rules used to determine oxidation number of an atom in a molecule is shown below.

• For each atom in its elemental state, the oxidation number is zero.

• For a monoatomic ion, the oxidation number is same as the charge on that species.

• The oxidation number of combined oxygen is $-2$ and for hydrogen is $+1$.

• The sum of oxidation numbers in a molecule or polyatomic ion or molecule is equal to the overall charge on the species.