Question

Define oxidation and reduction in terms of both change in oxidation number and electron loss or gain.

Short answer

Oxidation is a process involving the loss of electrons and an increase in oxidation number, whereas reduction involves the gain of electrons and a decrease in oxidation number. In a redox reaction, oxidation and reduction occur simultaneously. For example, in the reaction \(2Na + Cl_2 \rightarrow 2NaCl\), the sodium atom undergoes oxidation as its oxidation number increases from 0 to +1 due to electron loss, while the chlorine molecule undergoes reduction as its oxidation number decreases from 0 to -1 due to electron gain.

Step-by-step solution

1. Definition of Oxidation and Reduction

Oxidation and reduction are two processes that occur hand in hand, forming an essential part of any redox (reduction-oxidation) reaction. Oxidation is the process that involves a loss of electrons while reduction is the process that involves a gain of electrons.

2. Oxidation in terms of change in oxidation number

In chemical reactions, the oxidation numbers of the elements in a compound or an ion can change. When the oxidation number of an element increases, that is called oxidation. Oxidation occurs when an atom loses one or more electrons in a reaction, leading to a more positive oxidation state. For example, consider the following reaction: \(2Na + Cl_2 \rightarrow 2NaCl\) Here, the sodium atom (Na) goes from an oxidation number of 0 to +1, indicating that it has lost one electron, which results in its oxidation.

3. Reduction in terms of change in oxidation number

Reduction, on the other hand, is the process where the oxidation number of an element decreases. This happens when an atom gains one or more electrons in a reaction, leading to a less positive or more negative oxidation state. For example, in the same reaction as mentioned above: \(2Na + Cl_2 \rightarrow 2NaCl\) The chlorine molecule (Cl_2) goes from an oxidation number of 0 to -1 in the chloride ion (Cl−), indicating that it has gained one electron, which leads to its reduction.

4. Oxidation in terms of electron loss

Oxidation is the process in which an atom or ion loses one or more electrons from its valence shell (outermost shell). This results in an increase in the atom's positive charge or a decrease in its negative charge. As mentioned earlier, when electron loss takes place, the oxidation number of the element involved in the reaction increases.

5. Reduction in terms of electron gain

Reduction is the process in which an atom or ion gains one or more electrons in its valence shell. This results in a decrease in the atom's positive charge or an increase in its negative charge. As mentioned earlier, when electron gain takes place, the oxidation number of the element involved in the reaction decreases. In summary, oxidation and reduction involve changes in oxidation numbers, with oxidation being characterized by an increase in oxidation number due to electron loss, while reduction is characterized by a decrease in oxidation number due to electron gain. These two processes always occur simultaneously in a redox reaction.