Which term describes a reaction in which electrons are transferred between species?

• A. Activation Energy
• B. Half-Reactions
• C. Redox
• D. Spontaneous

Answer: (C)

Redox reactions involve the transfer of electrons between species. In a redox process, one species loses electrons (oxidation) and another gains electrons (reduction), so the overall reaction is defined by electron transfer from the donor to the acceptor. Writing half-reactions helps visualize the electron flow, but the key idea is that electrons are moved from one species to another, which is captured by the term redox. Activation energy is the energy barrier to reaction, not about electron transfer. Spontaneous describes whether a reaction can proceed without external input under given conditions, a thermodynamic property rather than the electron-transfer mechanism. Half-reactions are a useful representation of the two parts of the process, but redox best describes the overall reaction that involves electron transfer.