Radioactivity is radioactivity that is done by exposing a stable substance to radiation to become unstable and therefore radioactive. Most of the radioactivity does not produce other radioactive materials. This radioactivity was discovered by Irene Joliot-Curie and Frederick Joliot-Curie in 1934. It is artificial (man-made) radioactivity. Irene and Frederick showed that when lighter elements such as aluminum and boron are bombarded with α particles, the radiation continues to be emitted, even after the α source is removed. They also showed that the radiation is caused by emissions from particles that carry a single positive electrical charge with a mass equal to the mass of the electron. .
