Final answer:
Atoms have the highest energy at the c. transition state stage of a reaction.
Step-by-step explanation:
During a chemical reaction, atoms reach their highest energy state at the transition state. This fleeting phase occurs as reactants transform into products, involving the breaking and forming of chemical bonds. The transition state represents a moment of maximum potential energy, where bonds are in flux. It is crucial for understanding reaction mechanisms.
Reactants have lower energy, while products stabilize at a lower energy level. The transition state serves as a critical point where atoms undergo significant changes, and the reaction's fate is determined. This concept is fundamental in the study of reaction kinetics and thermodynamics in chemistry.