What refers to the number of electrons an atom has gained, lost, or shared in a chemical bond?

The oxidation number refers to the number of electrons that an atom has gained, lost, or shared in a chemical bond. This concept is integral to understanding how atoms interact in chemical reactions and the overall charge of molecules. The oxidation number helps categorize elements in compounds, allowing chemists to determine the type of bond formed between atoms (ionic or covalent) and predict the behavior of substances during reactions.

For example, in a compound, a positive oxidation number indicates that an atom has lost electrons, while a negative oxidation number suggests it has gained electrons. This information is essential in predicting how compounds will react with each other, as it relates directly to the distribution of electrons.

Other choices do not accurately describe the concept in question. Valence electrons pertain to the electrons in the outermost shell that participate in bonding, but they do not account for the specific gain or loss of electrons. Atomic mass quantifies the mass of an atom typically expressed in atomic mass units and does not provide insight into electron behavior. Molecular weight is a measure of the mass of a molecule based on its constituent atoms but again does not connect to electron gain or loss in bonding scenarios. Therefore, the most precise term that encapsulates the idea of electrons involved in chemical bonding is the oxidation