Final answer:
Marie Curie impacted the development of atomic theory through her research on radioactivity, discovering two new radioactive elements and contributing to the understanding of atomic structure.
Step-by-step explanation:
Marie Curie impacted the development of atomic theory through her research on radioactivity. She, along with her husband Pierre Curie, discovered two new radioactive elements, polonium and radium. This discovery filled holes in the periodic table and displayed much higher levels of radioactivity per gram of material than uranium. Marie Curie's research and contribution to the understanding of radioactivity contributed to the understanding of atomic structure.