Final answer:
Marie Curie discovered the phenomenon of radioactivity in certain elements like uranium, leading her to isolate two new elements, polonium and radium, which are significantly more radioactive than uranium. These discoveries were crucial to understanding the structure of the atomic nucleus and the nature of radioactive emissions.
Step-by-step explanation:
Marie Curie, alongside her husband Pierre Curie, made groundbreaking discoveries related to radioactivity. They discovered that certain elements, like uranium, naturally emitted radiation which was indicative of processes occurring at the atomic nucleus level. Through meticulous research, Marie Curie found that this radioactive emission does not change with the chemical state of the element, nor does it vary with temperature or pressure. These findings implied that the radiation was linked to the atomic nucleus and much more powerful than atomic energies typical in chemical reactions. Among their most significant accomplishments was the isolation of two new elements: polonium and radium. Polonium was named after Marie Curie's native Poland, while radium was so named for its intense radioactivity. Their work with radium led to the discovery that it was approximately two million times as radioactive as uranium, and it glowed visibly due to the radiation it emitted.