What does the oxidation number of an atom represent?

The oxidation number of an atom is a useful concept in chemistry that represents the hypothetical charge that an atom would have if all bonds to atoms of different elements were fully ionic. This means that the oxidation number reflects how many electrons an atom has gained, lost, or shared when it forms chemical bonds. It provides insight into the electron distribution of an atom in a compound, indicating whether the atom is in a more oxidized or reduced state.

By assigning oxidation numbers, chemists can track electron transfer in redox reactions, understand the behavior of substances in reactions, and predict the kind of ions that might form. For example, in a molecule like water (H₂O), oxygen has an oxidation number of -2, indicating that it has gained two electrons compared to its elemental state. This charge is derived from the electron distribution between hydrogen and oxygen atoms in the molecule.

This understanding of electron distribution is essential in predicting the reactivity and properties of different chemical species. So, the correct choice clearly links the oxidation number to the charge an atom appears to have based on its electron configuration relative to other elements it interacts with.