Which of the following best describes what happens during a redox reaction?

• A. Electrons are transferred from one species to another.
• B. Protons are exchanged between reactants.
• C. Energy is absorbed but no chemical bonds are broken.
• D. Atoms are rearranged without any change in electron distribution.

Answer: (A)

Verified step by step guidance

1. Understand that a redox reaction involves changes in the oxidation states of atoms, which means electrons are either lost or gained by species involved.
2. Recall that oxidation is the loss of electrons and reduction is the gain of electrons; these two processes always occur together in a redox reaction.
3. Recognize that protons (H⁺ ions) are not necessarily transferred in redox reactions; proton transfer is characteristic of acid-base reactions, not redox.
4. Note that energy absorption without bond breaking describes physical or some endothermic processes, but redox reactions specifically involve electron transfer and changes in chemical bonds.
5. Conclude that the defining feature of a redox reaction is the transfer of electrons from one species to another, which changes their oxidation states.