: An element is considered radioactive if its atoms' nuclei are unstable and release energy in the form of particles or electromagnetic waves.
: You can follow the Timeline of chemical element discoveries on Wikipedia to see when radioactive elements like Polonium and Radium were first identified by scientists like Marie and Pierre Curie. Examples of Radioactive Elements Radioaktiv Elementler Wikipedia
: Elements typically decay by emitting alpha , beta , or gamma radiation. : An element is considered radioactive if its
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