The modern understanding of ionizing radiation got its start in 1895 with Wilhelm Röntgen. he discovered that, despite covering one in a screen to block light, there seemed to be rays penetrating through to react with a barium solution on a screen he’d placed nearby. he named them “X-Rays” temporarily as a designation of something unknown, and the name stuck.
This discovery was followed in 1896 by Henri Becquerel’s discovery that Uranium(U) salts gave off similar rays naturally. Though originally thinking that the rays were given off by phosphorescent Uranium salts after prolonged exposure to the sun, he eventually abandoned this hypothesis.
Although it was Henri Becquerel that discovered the phenomenon, it was his doctoral student, Marie Curie, who named it: radioactivity. She would go on to do much more pioneering work with radioactive materials, including the discovery of additional radioactive elements: Thorium,(Th) Polonium(Po), and Radium(Ra). She was awarded the Nobel Prize twice, once alongside Henri Becquerel and her husband Pierre in Physics for their work with radioactivity, and again years later in Chemistry for her discovery of radium and polonium.
Watch the following video: