jan 1, 1898 - MARIE CURIE (1867-1934 CE)
date of discovery (1898 CE)
Atom is composed of particles
and the nuclei of heavy, unstable
elements lose mass (decay) and
give off energy (radioactivity).
Discovered unknown elements
polonium and radium and deduced
that radioactivity does not depend
on how atoms are arranged into
molecules, but rather that it originates
within the atoms themselves.