The discovery of radioactivity in uranium by French physicist Henri Becquerel in 1896 forced scientists to radically change their ideas about atomic structure. Radioacitivty demonstrated that the atom was neither indivisible nor immutable. Instead serving as an inert for electrons, the atom could change an enormous amount of energy. Radioactivity itself became an important tool for revealing the interior of the atom.

How can Radoactive isopotes be used in medicine. Radioactive isotopes, are species of chemical elements that are produced through the natural decay of atoms. Exposure to radiation is genearlly considered harmful to the human body but radioisotpes are highly valuable in medicine, particularly in the diagnosis and treatment of disease. Nuclear medicine uses radioactivity isotopes in a variety of ways. One of the most common ones uses a tracer in which a radioisotope like technetium-99m is taken or is injected or inhailed into the human body. The radioactive isotope then circulates through the body or is taken up only by certain tissues. Its distrivution can be trakced according to the radiation it gives off.