Question

Which of the following involves reduction:
A.Conversion of anion to atom
B.Conversion of cation to atom
C.Both of these
D.None of these

Answer 1

Hint:To answer this question, you should recall the concept of oxidation numbers. The oxidation state of an atom is defined as the number of electrons lost and, therefore, describes the extent of oxidation of the atom. For example, the oxidation state of carbon in\[{\text{C}}{{\text{O}}_{\text{2}}}\] would be $ + 4$ since the hypothetical charge held by the carbon atom if both of the carbon-oxygen double bonds were completely ionic would be equal to $ + 4$ .

Complete step by step answer:
The most frequent terms Oxidation state and oxidation number are terms frequently used interchangeably. They are defined and described as the number of electrons lost in an atom. The values can be zero, positive, or negative. These two processes are defined as:

Oxidation involves	Reduction involves
Losing electrons	Gaining electrons
Increase in oxidation number	A decrease in oxidation number
For a given compound losing hydrogen	For a given compound gaining hydrogen

Conversion of cation to atom involves gaining of electrons. Since cation is positively charged and the oxidation of an atom is zero, thus the oxidation no. is reduced, i.e., electrons are accepted and thus it involves reduction.

Hence, we conclude that the correct answer to this question is option B.

Note:
In most of the compounds, the oxidation number of oxygen is $ - 2$ . There are three exceptions here:
1.Peroxides: Each oxygen atom exhibits an oxidation number of $ - 1$ . Example, \[N{a_2}{O_2}\]
2.Superoxide- Every oxygen atom is allocated an oxidation number of \[ - \dfrac{1}{2}\] . Example, \[K{O_2}\]
Oxygen is bonded to fluorine- Example, dioxygen difluoride where the oxygen atom is allocated an oxidation number of $ + 1$ .