Which term refers to the number indicating how many electrons an atom will gain or lose during a reaction?

The term that accurately describes the number indicating how many electrons an atom will gain or lose during a reaction is oxidation numbers. This concept is crucial in understanding redox reactions, where the transfer of electrons occurs. Oxidation numbers are assigned to atoms in a compound based on a set of rules that help determine the degree of oxidation or reduction that an element undergoes.

For example, in a reaction where sodium (Na) donates an electron to form a sodium ion (Na⁺), its oxidation number changes from 0 in elemental form to +1 after electron loss. This change in oxidation number allows us to understand the underlying electron transfer during the chemical reaction.

Other terms are not used to describe the specific process of gaining or losing electrons in reactions. Radical numbers refer to unpaired electrons, ionic charges can describe ions but do not specify the number in a general sense, and electron counts would indicate the number of electrons in an atom but do not highlight their transfer in reactions. Hence, oxidation numbers are the most accurate term for this context.