Whose discovery of radium changed the worlds view of that atom

I don't know why this in English, but Marie Curie and her husband were examining rock (I forgot what type it was, but if I remember, I will send it's name to : D) and knew that it contained Uranium, but found that it was emitting way too high levels compared to Uranium would actually emit (through alpha decay), especially since Uranium existed in such small quantities in that rock in the first place. They soon found that a new element existed far more unstable and radioactive than Uranium called radium. They also discovered Polonium.

Marie Curie is the most notable discover, although her husband, Pierre Curie, contributed. It is very very unlikely that Pierre will be mentioned for any class however.