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Oxidation is a chemical reaction where a species loses electrons. This process can also be defined as an increase in the oxidation state of the species participating in the reaction. An oxidation state, also known as an oxidation number, is an integer representing the number of electrons that an element can lose, gain, or share when forming chemical bonds with other elements.

When a species loses an electron during a chemical reaction, its oxidation state increases. This occurs because the number of positively charged protons in the species now outnumbers the negatively charged electrons, indicating a more positive overall charge. Conversely, if the species gains an electron, its oxidation state decreases, thus balancing the charge of protons and electrons. Therefore, the loss of electrons or an increase in oxidation state represent the same concept, as both indicate that the species involved in the reaction is being oxidized.

Consider the redox reaction between magnesium and oxygen, which forms magnesium oxide (MgO): \[ \text{Mg} + \frac{1}{2}\text{O}_2 \rightarrow \text{MgO} \] In this reaction, magnesium (Mg) is oxidized while oxygen (O) is reduced: a. Oxidation: The Mg atom loses 2 electrons to form the Mg^2+ ion. This process increases the magnesium oxidation state from 0 to +2, which corresponds to a loss of 2 electrons: \[ \text{Mg} \rightarrow \text{Mg}^{2+} + 2e^- \] b. Reduction: The O atom gains 2 electrons to form the O^2- ion. This process results in a decrease of the oxygen oxidation state from 0 to -2, which corresponds to a gain of 2 electrons: \[ \frac{1}{2}\text{O}_2 + 2e^- \rightarrow \text{O}^{2-} \] Thus, the two definitions of oxidation become interchangeable in this example, as magnesium's increase in oxidation state from 0 to +2 signifies the loss of 2 electrons.