What role did Marie Curie play in the theory of radioactivity?

The fascinating article "Röntgen, Curie and Einstein: the beginning of trouble for physics?" by Giorgio Margaritondo (September p15) raises an important issue: what was the role of Marie Curie in the birth of modern physics? Margaritondo quotes a paper of Curie and colleagues (Comptes Rendus 127 1215) as proof that Curie considered radioactivity to be an atomic phenomenon in which "each one of the individual atoms 'decides' for its own mysterious reasons to radioactively decay at a certain time, in a totally unpredictable way."