Question

Why is it that when something gains electrons, it is said to be reduced? What is being reduced?

Short answer

In a redox reaction, when a species gains electrons, it is said to be reduced because its oxidation state decreases, signifying a reduction in its level of oxidation. The term "reduced" means the decrease in the oxidation state of a chemical species due to electron gain. What is being reduced is the oxidation state of the species, making it less oxidized.

Step-by-step solution

Understand Reduction and Oxidation

Reduction and oxidation, also known as redox reactions, are chemical processes that involve the transfer of electrons between two species. In a redox reaction, one species gains electrons (reduction) while the other species loses electrons (oxidation).

Identify the Reduced Species

In a chemical reaction, the species gaining electrons is termed as the reduced species. This is because when a species gains electrons, it experiences an increase in its negative charge. It means that the oxidation state (a measure of the degree of oxidation of an atom in a chemical compound) has decreased. For example, consider the following reaction: \[Cu^{2+ (aq)} + 2e^- \rightarrow Cu(s)\] In this case, the copper ion (Cu²⁺) gains 2 electrons (2e⁻) and is reduced to a solid copper metal (Cu). As you can see, the oxidation state of copper decreases from +2 to 0, that means it has experienced reduction.

Define "Reduced" in the Context of Reduction

The term "reduced" in the context of a redox reaction refers to the decrease in the oxidation state of a chemical species when it gains electrons. In other words, "reduced" essentially means the decrease in the level of oxidation of that species due to the electron gain.

Explain What is Being Reduced

In a redox reaction, what is being reduced is the oxidation state of the species. As a species gains electrons, its oxidation state decreases, making it less oxidized and therefore "reduced". In summary, when a species gains electrons in a chemical reaction, it is said to be "reduced" because the process leads to a decrease in its oxidation state. This change signifies a reduction in its level of oxidation.