In an oxidation-reduction (redox) reaction, what does an atom gain or lose to change its oxidation number?

• A. Neutrons
• B. Protons
• C. Electrons
• D. Energy

Answer: (C)

Verified step by step guidance

1. Understand that oxidation-reduction (redox) reactions involve the transfer of electrons between atoms or ions.
2. Recall that the oxidation number of an atom changes when it either loses or gains electrons during the reaction.
3. Recognize that protons and neutrons remain constant in the nucleus and do not change during redox reactions, so they do not affect the oxidation number.
4. Conclude that the key particle involved in changing the oxidation number is the electron, which can be lost (oxidation) or gained (reduction).
5. Therefore, in a redox reaction, an atom changes its oxidation number by gaining or losing electrons.