Which term refers to the separate oxidation or reduction steps that together compose a redox reaction?

• A. Half-Reactions
• B. Activated Complex
• C. Spectator Ion
• D. Spontaneous

Answer: (A)

Redox reactions are built from two half-reactions, one showing what gets oxidized and one showing what gets reduced. Each half-reaction tracks the transfer of electrons, and we balance them separately before combining them so the electrons cancel. That separation into an oxidation step and a reduction step is exactly what “half-reactions” refers to. The other terms don’t describe this two-step electron transfer process: an activated complex is the high-energy, transient arrangement along a reaction path; a spectator ion is present but not participating in the change; spontaneous describes whether a reaction can occur without added energy, not how the reaction is divided into steps.