The oxidation number, also known as the oxidation state, is a measure of the degree of oxidation of an atom in a chemical compound. It represents the number of electrons that an atom has lost or gained relative to a neutral atom of the same element.
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Oxidation numbers are assigned based on a set of rules and conventions, which help determine the charge on an atom in a compound.
Atoms in their elemental form have an oxidation number of 0, while ions have an oxidation number equal to their charge.
Hydrogen has an oxidation number of +1, except when bonded to metals in binary compounds, where it has an oxidation number of -1.
Oxygen typically has an oxidation number of -2, except in peroxides (where it is -1) and in compounds with fluorine (where it is positive).
The sum of the oxidation numbers in a neutral compound is 0, while in an ion, the sum of the oxidation numbers equals the charge of the ion.
Review Questions
Explain how oxidation numbers are used to determine the degree of oxidation or reduction in a chemical reaction.
Oxidation numbers are used to track the flow of electrons in a chemical reaction. When a substance is oxidized, its oxidation number increases, indicating that it has lost electrons. Conversely, when a substance is reduced, its oxidation number decreases, indicating that it has gained electrons. By comparing the changes in oxidation numbers between the reactants and products, you can identify the oxidation and reduction processes occurring in a redox reaction.
Describe the role of oxidation numbers in understanding the structure and bonding of organic compounds.
Oxidation numbers are particularly important in organic chemistry, as they help determine the formal charge on atoms within a molecule. This information can provide insights into the stability and reactivity of the compound. For example, understanding the oxidation numbers of carbon, hydrogen, and oxygen atoms in an organic molecule can help predict the likelihood of oxidation or reduction reactions occurring, as well as the potential for functional group interconversions.
Evaluate how the assignment of oxidation numbers can be used to identify and balance redox reactions in organic chemistry.
By assigning and tracking the changes in oxidation numbers of atoms in an organic reaction, you can determine which substances are being oxidized and which are being reduced. This information is crucial for balancing redox reactions, as the number of electrons lost by the oxidized species must equal the number of electrons gained by the reduced species. Properly balancing redox reactions in organic chemistry is essential for understanding reaction mechanisms and predicting the products of transformations involving oxidation and reduction.