Neutron

Enrico Fermi (1901-1954), a young Italian scientist, constructed a neutron source according to Chadwick's design, mixing radium and beryllium powder together in a small glass tube. Fermi's plan was to use this neutron source for making new radioactive materials. Together with his co-workers, he was successful in producing radioactive sodium, iron, copper, gold, and many other elements. Fermi received the l938 Nobel Prize in physics for his work with neutrons.

Almost all elements found in nature can now be made radioactive. Radioactive potassium and phosphorus are used as tracers to measure how effectively plants take up fertilizer from soil. Radioactive iodine is applied in nuclear medicine to diagnose and treat thyroid problems. Radiation treatment for cancer therapy uses radioactive cobalt, which is made by irradiating ordinary cobalt with neutrons.